diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -11,6 +11,7 @@
 #include <crypto/sha256.h>
 #include <primitives/transaction.h>
 #include <pubkey.h>
+#include <reverse_iterator.h>
 #include <script/script.h>
 #include <script/script_flags.h>
 #include <script/sigencoding.h>
@@ -1006,62 +1007,136 @@
                                 serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
                         }
 
-                        // A bug causes CHECKMULTISIG to consume one extra
-                        // argument whose contents were not checked in any way.
-                        //
-                        // Unfortunately this is a potential source of
-                        // mutability, so optionally verify it is exactly equal
-                        // to zero.
-                        if ((flags & SCRIPT_VERIFY_NULLDUMMY) &&
-                            stacktop(-idxDummy).size()) {
-                            return set_error(serror, SCRIPT_ERR_SIG_NULLDUMMY);
-                        }
-
                         // Subset of script starting at the most recent
                         // codeseparator
                         CScript scriptCode(pbegincodehash, pend);
 
-                        // Remove signature for pre-fork scripts
-                        for (int k = 0; k < nSigsCount; k++) {
-                            valtype &vchSig = stacktop(-idxTopSig - k);
-                            CleanupScriptCode(scriptCode, vchSig, flags);
-                        }
-
                         bool fSuccess = true;
                         int nSigsRemaining = nSigsCount;
                         int nKeysRemaining = nKeysCount;
-                        while (fSuccess && nSigsRemaining > 0) {
-                            valtype &vchSig = stacktop(
-                                -idxTopSig - (nSigsCount - nSigsRemaining));
-                            valtype &vchPubKey = stacktop(
-                                -idxTopKey - (nKeysCount - nKeysRemaining));
-
-                            // Note how this makes the exact order of
-                            // pubkey/signature evaluation distinguishable by
-                            // CHECKMULTISIG NOT if the STRICTENC flag is set.
-                            // See the script_(in)valid tests for details.
-                            if (!CheckTransactionECDSASignatureEncoding(
-                                    vchSig, flags, serror) ||
-                                !CheckPubKeyEncoding(vchPubKey, flags,
-                                                     serror)) {
-                                // serror is set
-                                return false;
+
+                        if ((flags & SCRIPT_ENABLE_SCHNORR_MULTISIG) &&
+                            (stacktop(-idxDummy).size() != 0)) {
+                            // NEW MULTISIG (SCHNORR / NULL)
+
+                            // Dummy element is to be interpreted as a bitfield
+                            // that represent which pubkeys should be checked.
+                            valtype &vchDummy = stacktop(-idxDummy);
+
+                            // Its byte-length must be the minimum to hold
+                            // nPubKeys bits.
+                            if (vchDummy.size() !=
+                                size_t((nKeysCount + 7) / 8)) {
+                                return set_error(serror,
+                                                 SCRIPT_ERR_INVALID_CHECKBITS);
                             }
 
-                            // Check signature
-                            bool fOk = checker.CheckSig(vchSig, vchPubKey,
-                                                        scriptCode, flags);
+                            static_assert(MAX_PUBKEYS_PER_MULTISIG <= 32);
+                            uint32_t checkBits = 0;
+
+                            // Decode the bitfield (little-endian)
+                            for (uint8_t b : reverse_iterate(vchDummy)) {
+                                checkBits = (checkBits << 8) | b;
+                            }
 
-                            if (fOk) {
+                            for (; nSigsRemaining > 0 && nKeysRemaining > 0;
+                                 checkBits >>= 1, nKeysRemaining--) {
+                                if ((checkBits & 1) == 0) {
+                                    continue;
+                                }
+                                valtype &vchSig = stacktop(
+                                    -idxTopSig - (nSigsCount - nSigsRemaining));
+                                valtype &vchPubKey = stacktop(
+                                    -idxTopKey - (nKeysCount - nKeysRemaining));
+                                if (!CheckTransactionSchnorrSignatureEncoding(
+                                        vchSig, flags, serror) ||
+                                    !CheckPubKeyEncoding(vchPubKey, flags,
+                                                         serror)) {
+                                    // serror is set
+                                    return false;
+                                }
+                                if (!checker.CheckSig(vchSig, vchPubKey,
+                                                      scriptCode, flags)) {
+                                    // It is forbidden to request an invalid
+                                    // signature.
+                                    return set_error(
+                                        serror,
+                                        vchSig.size()
+                                            ? SCRIPT_ERR_SIG_NULLFAIL
+                                            : SCRIPT_ERR_INVALID_CHECKBITS);
+                                }
+                                // A successful checksig is the only way to
+                                // decrement nSigsRemaining.
                                 nSigsRemaining--;
                             }
-                            nKeysRemaining--;
+                            if (nSigsRemaining > 0) {
+                                // Ended before checking all signatures, because
+                                // too few bits were set.
+                                return set_error(serror,
+                                                 SCRIPT_ERR_INVALID_CHECKBITS);
+                            }
+                            if (checkBits != 0) {
+                                // Ended before consuming all bits, because too
+                                // many bits were set or a too-high bit was set.
+                                return set_error(serror,
+                                                 SCRIPT_ERR_INVALID_CHECKBITS);
+                            }
+                        } else {
+                            // LEGACY MULTISIG (ECDSA / NULL)
+                            // A bug causes CHECKMULTISIG to consume one extra
+                            // argument whose contents were not checked in any
+                            // way.
+                            //
+                            // Unfortunately this is a potential source of
+                            // mutability, so optionally verify it is exactly
+                            // equal to zero.
+                            if ((flags & SCRIPT_VERIFY_NULLDUMMY) &&
+                                stacktop(-idxDummy).size()) {
+                                return set_error(serror,
+                                                 SCRIPT_ERR_SIG_NULLDUMMY);
+                            }
 
-                            // If there are more signatures left than keys left,
-                            // then too many signatures have failed. Exit early,
-                            // without checking any further signatures.
-                            if (nSigsRemaining > nKeysRemaining) {
-                                fSuccess = false;
+                            // Remove signature for pre-fork scripts
+                            for (int k = 0; k < nSigsCount; k++) {
+                                valtype &vchSig = stacktop(-idxTopSig - k);
+                                CleanupScriptCode(scriptCode, vchSig, flags);
+                            }
+
+                            while (fSuccess && nSigsRemaining > 0) {
+                                valtype &vchSig = stacktop(
+                                    -idxTopSig - (nSigsCount - nSigsRemaining));
+                                valtype &vchPubKey = stacktop(
+                                    -idxTopKey - (nKeysCount - nKeysRemaining));
+
+                                // Note how this makes the exact order of
+                                // pubkey/signature evaluation distinguishable
+                                // by CHECKMULTISIG NOT if the STRICTENC flag is
+                                // set. See the script_(in)valid tests for
+                                // details.
+                                if (!CheckTransactionECDSASignatureEncoding(
+                                        vchSig, flags, serror) ||
+                                    !CheckPubKeyEncoding(vchPubKey, flags,
+                                                         serror)) {
+                                    // serror is set
+                                    return false;
+                                }
+
+                                // Check signature
+                                bool fOk = checker.CheckSig(vchSig, vchPubKey,
+                                                            scriptCode, flags);
+
+                                if (fOk) {
+                                    nSigsRemaining--;
+                                }
+                                nKeysRemaining--;
+
+                                // If there are more signatures left than keys
+                                // left, then too many signatures have failed.
+                                // Exit early, without checking any further
+                                // signatures.
+                                if (nSigsRemaining > nKeysRemaining) {
+                                    fSuccess = false;
+                                }
                             }
                         }
 
diff --git a/src/script/script_error.h b/src/script/script_error.h
--- a/src/script/script_error.h
+++ b/src/script/script_error.h
@@ -25,6 +25,7 @@
     SCRIPT_ERR_INVALID_NUMBER_RANGE,
     SCRIPT_ERR_IMPOSSIBLE_ENCODING,
     SCRIPT_ERR_INVALID_SPLIT_RANGE,
+    SCRIPT_ERR_INVALID_CHECKBITS,
 
     /* Failed verify operations */
     SCRIPT_ERR_VERIFY,
diff --git a/src/script/script_error.cpp b/src/script/script_error.cpp
--- a/src/script/script_error.cpp
+++ b/src/script/script_error.cpp
@@ -45,6 +45,8 @@
             return "The requested encoding is impossible to satisfy";
         case SCRIPT_ERR_INVALID_SPLIT_RANGE:
             return "Invalid OP_SPLIT range";
+        case SCRIPT_ERR_INVALID_CHECKBITS:
+            return "Invalid checkbits value in OP_CHECKMULTISIG";
         case SCRIPT_ERR_BAD_OPCODE:
             return "Opcode missing or not understood";
         case SCRIPT_ERR_DISABLED_OPCODE:
diff --git a/src/test/data/script_tests.json b/src/test/data/script_tests.json
--- a/src/test/data/script_tests.json
+++ b/src/test/data/script_tests.json
@@ -3004,6 +3004,188 @@
     "SIG_BADLENGTH",
     "recovered-pubkey CHECKMULTISIG with 64-byte DER w/ SCHNORR_MULTISIG"
 ],
+[
+    "1 0x41 0x105e4fed395e64ca013ac1ce020ef69b9990a577fe4b74648faafb69e499f76dd53d5c64aa866924361dd3aadde9b7184bbcb4f79520396c9ed17c4d8489a59701",
+    "1 0x41 0x0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8 1 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 1-of-1"
+],
+[
+    "0x02 0x0100 0x41 0x105e4fed395e64ca013ac1ce020ef69b9990a577fe4b74648faafb69e499f76dd53d5c64aa866924361dd3aadde9b7184bbcb4f79520396c9ed17c4d8489a59701",
+    "1 0x41 0x0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8 1 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 1-of-1 nonminimal bits"
+],
+[
+    "7 0x41 0x833682d4f60cc916a22a2c263e658fa662c49badb1e2a8c6208987bf99b1abd740498371480069e7a7a6e7471bf78c27bd9a1fd04fb212a92017346250ac187b01 0x41 0xea4a8d20562a950f4695dc24804565482e9fa111704886179d0c348f2b8a15fe691a305cd599c59c131677146661d5b98cb935330989a85f33afc70d0a21add101 0x41 0xce9011d76a4df05d6280b2382b4d91490dbec7c3e72dc826be1fc9b4718f627955190745cac96521ea46d6d324c7376461e225310e6cd605b9f266d170769b7901",
+    "3 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 3-of-3"
+],
+[
+    "15 0x41 0x6d1d1f8db2b4e43a51b4f5f16367045f9c1832b8103ce2bab3a21afc223351a685e84bca02c863110e7ad22d4735cd31e1908e741530e3a07863292c3ff21df901 0x41 0x6d1d1f8db2b4e43a51b4f5f16367045f9c1832b8103ce2bab3a21afc223351a685e84bca02c863110e7ad22d4735cd31e1908e741530e3a07863292c3ff21df901 0x41 0x98ac816c0adb14db2a593f6402bf70e347a219fba0ccad805a5e37a67e265c800b1d493440965634fe740852fbe4164ec45a722a463099ae8a9872896da972ef01 0x41 0xe62867a73ae91b390f6ae11717d360fbc7e813a6dc3917040556834350d5b3cfb464e7222a716f37a32ba3fee353ad4957aa3f47cf7ea1285873bc9a0e64759801",
+    "4 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "SIG_COUNT",
+    "New-CHECKMULTISIG 4-of-3"
+],
+[
+    "6 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 2-of-3 (110)"
+],
+[
+    "5 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101 0x41 0xa3fac6b1aa2cc8bb222ee379711c243b26a164ced7f2e2f4a0e184a3e53352bfaee598c6446861e5a7e819871b7ce948f5562ecf214c19dfa5112c19d74adc7101",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 2-of-3 (101)"
+],
+[
+    "3 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001 0x41 0xa3fac6b1aa2cc8bb222ee379711c243b26a164ced7f2e2f4a0e184a3e53352bfaee598c6446861e5a7e819871b7ce948f5562ecf214c19dfa5112c19d74adc7101",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 2-of-3 (011)"
+],
+[
+    "3 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101 0x41 0xa3fac6b1aa2cc8bb222ee379711c243b26a164ced7f2e2f4a0e184a3e53352bfaee598c6446861e5a7e819871b7ce948f5562ecf214c19dfa5112c19d74adc7101",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "NULLFAIL",
+    "New-CHECKMULTISIG 2-of-3 mismatched bits"
+],
+[
+    "7 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001 0x41 0xa3fac6b1aa2cc8bb222ee379711c243b26a164ced7f2e2f4a0e184a3e53352bfaee598c6446861e5a7e819871b7ce948f5562ecf214c19dfa5112c19d74adc7101",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 2-of-3 all bits set"
+],
+[
+    "14 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 2-of-3 extra high bit set"
+],
+[
+    "10 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 2-of-3 too high bit set"
+],
+[
+    "2 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 2-of-3 too few bits set"
+],
+[
+    "0x01 0x00 0 0",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 2-of-3 with no bits set (attempt to malleate return-false)"
+],
+[
+    "0 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "SIG_BADLENGTH",
+    "CHECKMULTISIG null dummy with schnorr sigs (with SCRIPT_ENABLE_SCHNORR_MULTISIG on)"
+],
+[
+    "6 0x41 0x4829a4df8042001ba6a3ee6ec1e9c26de662aade55a49f8d018acff0bac0df2edd881cf21f2a1aa651b6f703f0cde22fedaa9b8bc3451101bcac37bcb89dcc8001 0x41 0xb8c744ebecfa75ef478b2b8852795d93b99640e5c05421ef6f651d4044be6cf2db2c61d0b5395e685731556c87e501433fb6e6a3b44c113d0ba19df8fd01c18101",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "NULLFAIL",
+    "New-CHECKMULTISIG 2-of-3 misordered signatures"
+],
+[
+    "-1 0x41 0x34b9918c9cd9aa3ad0f642f1dd435164e7bed979e539b2890b8d465b70db47385c514a21b1c6659ab40b8e5395ceae8f6c67c6f4c24e940cbe0a6fe496e7d15e01 0x41 0x057e3e62dbcf8a1bd3526271ad63f568bdae4d248bd87dfcf4a80b9f6da28e0994e04c670a56e624301141f53efc9a40f7d503171809e3f70d5aee203a90567d01",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 DUP 2DUP 2DUP 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 8 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 2-of-8 right way to represent 0b10000001"
+],
+[
+    "0x02 0x8100 0x41 0x34b9918c9cd9aa3ad0f642f1dd435164e7bed979e539b2890b8d465b70db47385c514a21b1c6659ab40b8e5395ceae8f6c67c6f4c24e940cbe0a6fe496e7d15e01 0x41 0x057e3e62dbcf8a1bd3526271ad63f568bdae4d248bd87dfcf4a80b9f6da28e0994e04c670a56e624301141f53efc9a40f7d503171809e3f70d5aee203a90567d01",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 DUP 2DUP 2DUP 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 8 CHECKMULTISIG",
+    "NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 2-of-8 wrong way to represent 0b10000001"
+],
+[
+    "0x03 0xffff0f 0x41 0x5f4f7ffff1fa44347dbc148d51fe661b60fbc44b5abe22a04d97ecfb891bdb2568eb91aa38a426dfd7b82e0b45b57af6f3e56143fabc850ebfdfcf6a0d03c4b001 0x41 0x28add881f6fa489a9016f066022ed80acecbafc351a6d17025cf87bf2b0d9b09f6d001f5df2b1be0d1909a8fe9280b59b5a8cb6d1e37425e733ff3267ce1e1b401 0x41 0x9f66f20bca4a64fc3cc170c3e1ef2bcb62f86b719b2f8e7154407e9210fde99164d754f787bf65020dc7db3838c8aae3591eaf465f45433fcb3d0a94bea4090401",
+    "OVER DUP DUP 2DUP 3DUP 3DUP 3DUP 3DUP 0x01 0x14 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 OVER DUP DUP 2DUP 3DUP 3DUP 3DUP 3DUP 0x01 0x14 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 20-of-20"
+],
+[
+    "0x03 0x000010 0x41 0x5f4f7ffff1fa44347dbc148d51fe661b60fbc44b5abe22a04d97ecfb891bdb2568eb91aa38a426dfd7b82e0b45b57af6f3e56143fabc850ebfdfcf6a0d03c4b001 0x41 0x28add881f6fa489a9016f066022ed80acecbafc351a6d17025cf87bf2b0d9b09f6d001f5df2b1be0d1909a8fe9280b59b5a8cb6d1e37425e733ff3267ce1e1b401 0x41 0x9f66f20bca4a64fc3cc170c3e1ef2bcb62f86b719b2f8e7154407e9210fde99164d754f787bf65020dc7db3838c8aae3591eaf465f45433fcb3d0a94bea4090401",
+    "OVER DUP DUP 2DUP 3DUP 3DUP 3DUP 3DUP 0x01 0x14 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 OVER DUP DUP 2DUP 3DUP 3DUP 3DUP 3DUP 0x01 0x14 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "CHECKBITS",
+    "New-CHECKMULTISIG 20-of-20 checkbits +1"
+],
+[
+    "0x03 0x000010 0x41 0xbe6635b93b92ff98d0d929d3537bf2941bbc33b9b4adc14d928e1b6eae1aa1fd23455e4094764f70dd896f47b3279b57965ecad1b4d32c1000be27be8cf83ece01",
+    "1 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 DUP 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 3DUP 3DUP 3DUP 3DUP 3DUP 3DUP 0x01 0x15 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "PUBKEY_COUNT",
+    "New-CHECKMULTISIG 1-of-21"
+],
+[
+    "0x03 0x000008 0x41 0x020fb4d03e4c7ea6e17f5a7d03c74a6cc33fd7f949d6bc5eb8f6122a4fa5a9bc208adafc7a92030fea664f044cccfd473b8ebaae94cd7bdeec8346a02ac0e3df01",
+    "1 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 DUP 2DUP 3DUP 3DUP 3DUP 3DUP 3DUP 0x01 0x14 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 1-of-20 bottom key"
+],
+[
+    "0x03 0x080000 0x41 0x020fb4d03e4c7ea6e17f5a7d03c74a6cc33fd7f949d6bc5eb8f6122a4fa5a9bc208adafc7a92030fea664f044cccfd473b8ebaae94cd7bdeec8346a02ac0e3df01",
+    "1 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 DUP 2DUP 3DUP 3DUP 3DUP 3DUP 3DUP 0x01 0x14 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "NULLFAIL",
+    "New-CHECKMULTISIG 1-of-20 bottom key; wrong endianness"
+],
+[
+    "3 0x41 0x3dfd744897afdad123edf671b9f7ad99f884cf714ada36f4c1cba12f7bdc71c6369832821a91964eb7d05552f1e32e5506d6dc2262e3ca5d1238690e3ddb075401 0x41 0x84aa5be4ebc905d6390a5be1b0101a0f2aab9563603a52c864db5deb459266cf1ea4376d378aa69a907a4e255919ecbff044d21b76dd004d34266c7ad8b84af501",
+    "2 0x02 0xbeef 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 2-of-3 (011), first key garbage"
+],
+[
+    "3 0x41 0x7e57eab163176c372e6f2baa2446998817b429d9cd8e3ee3a6841a95bf19fa128562848b590bf2ada480a23bbb6697f3e920594e7bf410b3b8af489862ee660601 0x41 0x64b53fe45bc169d53366fe20f7340596ba9ad86566ae725535e32c5a40d4d3dbd448bc898d0528395eca1c634e4ce422c856c6063cb947d8191127317da4a5a001",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x02 0xbeef 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "PUBKEYTYPE",
+    "New-CHECKMULTISIG 2-of-3 (011), last key garbage"
+],
+[
+    "6 0x41 0xb7aa94db79ecf22bdfd4d986ac4ba294fc044dd75696a6f95b12fef2dee48e02e06ccda571e0d513a03c585f86a8df1223a02556c11d7f1da71ba10544e9bc9501 0x41 0x3dfd744897afdad123edf671b9f7ad99f884cf714ada36f4c1cba12f7bdc71c6369832821a91964eb7d05552f1e32e5506d6dc2262e3ca5d1238690e3ddb075401",
+    "2 0x02 0xbeef 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "PUBKEYTYPE",
+    "New-CHECKMULTISIG 2-of-3 (110), first key garbage"
+],
+[
+    "6 0x41 0xc09a62bbf5b7e45503a682cc72559b4d060edf1144023b47e765375a8e0cb017da3b0b72e2912a772989ce922f7f298890e66ff9f36c813b872682fc6b95a04b01 0x41 0x7e57eab163176c372e6f2baa2446998817b429d9cd8e3ee3a6841a95bf19fa128562848b590bf2ada480a23bbb6697f3e920594e7bf410b3b8af489862ee660601",
+    "2 0x21 0x0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 0x21 0x038282263212c609d9ea2a6e3e172de238d8c39cabd5ac1ca10646e23fd5f51508 0x02 0xbeef 3 CHECKMULTISIG",
+    "MINIMALDATA,NULLFAIL,SCHNORR_MULTISIG,STRICTENC",
+    "OK",
+    "New-CHECKMULTISIG 2-of-3 (110), last key garbage"
+],
 
 ["CHECKSEQUENCEVERIFY tests"],
 ["", "CHECKSEQUENCEVERIFY", "CHECKSEQUENCEVERIFY", "INVALID_STACK_OPERATION", "CSV automatically fails on an empty stack"],
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -60,6 +60,7 @@
     {SCRIPT_ERR_INVALID_NUMBER_RANGE, "INVALID_NUMBER_RANGE"},
     {SCRIPT_ERR_IMPOSSIBLE_ENCODING, "IMPOSSIBLE_ENCODING"},
     {SCRIPT_ERR_INVALID_SPLIT_RANGE, "SPLIT_RANGE"},
+    {SCRIPT_ERR_INVALID_CHECKBITS, "CHECKBITS"},
     {SCRIPT_ERR_VERIFY, "VERIFY"},
     {SCRIPT_ERR_EQUALVERIFY, "EQUALVERIFY"},
     {SCRIPT_ERR_CHECKMULTISIGVERIFY, "CHECKMULTISIGVERIFY"},
@@ -1845,6 +1846,272 @@
                             .ScriptError(SCRIPT_ERR_SIG_BADLENGTH));
     }
 
+    // Tests of new-checkmultisig actually turned on (flag on & dummy element is
+    // not null).
+    tests.push_back(TestBuilder(CScript() << OP_1 << ToByteVector(keys.pubkey0)
+                                          << OP_1 << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 1-of-1", newmultisigflags)
+                        .Num(0b1)
+                        .PushSigSchnorr(keys.key0));
+    tests.push_back(TestBuilder(CScript() << OP_1 << ToByteVector(keys.pubkey0)
+                                          << OP_1 << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 1-of-1 nonminimal bits",
+                                newmultisigflags)
+                        .Push("0100")
+                        .PushSigSchnorr(keys.key0)
+                        .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(TestBuilder(CScript() << OP_3 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 3-of-3", newmultisigflags)
+                        .Num(0b111)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1)
+                        .PushSigSchnorr(keys.key2));
+    tests.push_back(TestBuilder(CScript() << OP_4 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 4-of-3", newmultisigflags)
+                        .Num(0b1111)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1)
+                        .PushSigSchnorr(keys.key2)
+                        .ScriptError(SCRIPT_ERR_SIG_COUNT));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 (110)",
+                                newmultisigflags)
+                        .Num(0b110)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 (101)",
+                                newmultisigflags)
+                        .Num(0b101)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key2));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 (011)",
+                                newmultisigflags)
+                        .Num(0b011)
+                        .PushSigSchnorr(keys.key1)
+                        .PushSigSchnorr(keys.key2));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 mismatched bits",
+                                newmultisigflags)
+                        .Num(0b011)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key2)
+                        .ScriptError(SCRIPT_ERR_SIG_NULLFAIL));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 all bits set",
+                                newmultisigflags)
+                        .Num(0b111)
+                        .PushSigSchnorr(keys.key1)
+                        .PushSigSchnorr(keys.key2)
+                        .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 extra high bit set",
+                                newmultisigflags)
+                        .Num(0b1110)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1)
+                        .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 too high bit set",
+                                newmultisigflags)
+                        .Num(0b1010)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1)
+                        .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 too few bits set",
+                                newmultisigflags)
+                        .Num(0b010)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1)
+                        .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 2-of-3 with no bits set "
+                                "(attempt to malleate return-false)",
+                                newmultisigflags)
+                        .Push("00")
+                        .Num(0)
+                        .Num(0)
+                        .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                                          << ToByteVector(keys.pubkey1C)
+                                          << ToByteVector(keys.pubkey2C) << OP_3
+                                          << OP_CHECKMULTISIG,
+                                "CHECKMULTISIG null dummy with schnorr sigs "
+                                "(with SCRIPT_ENABLE_SCHNORR_MULTISIG on)",
+                                newmultisigflags)
+                        .Num(0)
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1)
+                        .ScriptError(SCRIPT_ERR_SIG_BADLENGTH));
+    tests.push_back(
+        TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                              << ToByteVector(keys.pubkey1C)
+                              << ToByteVector(keys.pubkey2C) << OP_3
+                              << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 2-of-3 misordered signatures",
+                    newmultisigflags)
+            .Num(0b110)
+            .PushSigSchnorr(keys.key1)
+            .PushSigSchnorr(keys.key0)
+            .ScriptError(SCRIPT_ERR_SIG_NULLFAIL));
+    tests.push_back(
+        TestBuilder(
+            CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                      << ToByteVector(keys.pubkey1C) << OP_DUP << OP_2DUP
+                      << OP_2DUP << ToByteVector(keys.pubkey2C) << OP_8
+                      << OP_CHECKMULTISIG,
+            "New-CHECKMULTISIG 2-of-8 right way to represent 0b10000001",
+            newmultisigflags)
+            .Num(-1)
+            .PushSigSchnorr(keys.key0)
+            .PushSigSchnorr(keys.key2));
+    tests.push_back(
+        TestBuilder(
+            CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                      << ToByteVector(keys.pubkey1C) << OP_DUP << OP_2DUP
+                      << OP_2DUP << ToByteVector(keys.pubkey2C) << OP_8
+                      << OP_CHECKMULTISIG,
+            "New-CHECKMULTISIG 2-of-8 wrong way to represent 0b10000001",
+            newmultisigflags & ~SCRIPT_VERIFY_MINIMALDATA)
+            .Num(0b10000001)
+            .PushSigSchnorr(keys.key0)
+            .PushSigSchnorr(keys.key2)
+            .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(TestBuilder(CScript()
+                                    << OP_OVER << OP_DUP << OP_DUP << OP_2DUP
+                                    << OP_3DUP << OP_3DUP << OP_3DUP << OP_3DUP
+                                    << 20 << ToByteVector(keys.pubkey0C)
+                                    << ToByteVector(keys.pubkey1C)
+                                    << ToByteVector(keys.pubkey2C) << OP_OVER
+                                    << OP_DUP << OP_DUP << OP_2DUP << OP_3DUP
+                                    << OP_3DUP << OP_3DUP << OP_3DUP << 20
+                                    << OP_CHECKMULTISIG,
+                                "New-CHECKMULTISIG 20-of-20", newmultisigflags)
+                        .Push("ffff0f")
+                        .PushSigSchnorr(keys.key0)
+                        .PushSigSchnorr(keys.key1)
+                        .PushSigSchnorr(keys.key2));
+    tests.push_back(
+        TestBuilder(CScript()
+                        << OP_OVER << OP_DUP << OP_DUP << OP_2DUP << OP_3DUP
+                        << OP_3DUP << OP_3DUP << OP_3DUP << 20
+                        << ToByteVector(keys.pubkey0C)
+                        << ToByteVector(keys.pubkey1C)
+                        << ToByteVector(keys.pubkey2C) << OP_OVER << OP_DUP
+                        << OP_DUP << OP_2DUP << OP_3DUP << OP_3DUP << OP_3DUP
+                        << OP_3DUP << 20 << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 20-of-20 checkbits +1", newmultisigflags)
+            .Push("000010")
+            .PushSigSchnorr(keys.key0)
+            .PushSigSchnorr(keys.key1)
+            .PushSigSchnorr(keys.key2)
+            .ScriptError(SCRIPT_ERR_INVALID_CHECKBITS));
+    tests.push_back(
+        TestBuilder(CScript() << OP_1 << ToByteVector(keys.pubkey0C) << OP_DUP
+                              << ToByteVector(keys.pubkey1C) << OP_3DUP
+                              << OP_3DUP << OP_3DUP << OP_3DUP << OP_3DUP
+                              << OP_3DUP << 21 << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 1-of-21", newmultisigflags)
+            .Push("000010")
+            .PushSigSchnorr(keys.key0)
+            .ScriptError(SCRIPT_ERR_PUBKEY_COUNT));
+    tests.push_back(
+        TestBuilder(CScript() << OP_1 << ToByteVector(keys.pubkey0C)
+                              << ToByteVector(keys.pubkey1C) << OP_DUP
+                              << OP_2DUP << OP_3DUP << OP_3DUP << OP_3DUP
+                              << OP_3DUP << OP_3DUP << 20 << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 1-of-20 bottom key", newmultisigflags)
+            .Push("000008")
+            .PushSigSchnorr(keys.key0));
+    tests.push_back(
+        TestBuilder(CScript() << OP_1 << ToByteVector(keys.pubkey0C)
+                              << ToByteVector(keys.pubkey1C) << OP_DUP
+                              << OP_2DUP << OP_3DUP << OP_3DUP << OP_3DUP
+                              << OP_3DUP << OP_3DUP << 20 << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 1-of-20 bottom key; wrong endianness",
+                    newmultisigflags)
+            .Push("080000")
+            .PushSigSchnorr(keys.key0)
+            .ScriptError(SCRIPT_ERR_SIG_NULLFAIL));
+    tests.push_back(
+        TestBuilder(CScript() << OP_2 << ToByteVector(ParseHex("BEEF"))
+                              << ToByteVector(keys.pubkey1C)
+                              << ToByteVector(keys.pubkey2C) << OP_3
+                              << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 2-of-3 (011), first key garbage",
+                    newmultisigflags)
+            .Num(0b011)
+            .PushSigSchnorr(keys.key1)
+            .PushSigSchnorr(keys.key2));
+    tests.push_back(
+        TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                              << ToByteVector(keys.pubkey1C)
+                              << ToByteVector(ParseHex("BEEF")) << OP_3
+                              << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 2-of-3 (011), last key garbage",
+                    newmultisigflags)
+            .Num(0b011)
+            .PushSigSchnorr(keys.key1)
+            .PushSigSchnorr(keys.key2)
+            .ScriptError(SCRIPT_ERR_PUBKEYTYPE));
+    tests.push_back(
+        TestBuilder(CScript() << OP_2 << ToByteVector(ParseHex("BEEF"))
+                              << ToByteVector(keys.pubkey1C)
+                              << ToByteVector(keys.pubkey2C) << OP_3
+                              << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 2-of-3 (110), first key garbage",
+                    newmultisigflags)
+            .Num(0b110)
+            .PushSigSchnorr(keys.key0)
+            .PushSigSchnorr(keys.key1)
+            .ScriptError(SCRIPT_ERR_PUBKEYTYPE));
+    tests.push_back(
+        TestBuilder(CScript() << OP_2 << ToByteVector(keys.pubkey0C)
+                              << ToByteVector(keys.pubkey1C)
+                              << ToByteVector(ParseHex("BEEF")) << OP_3
+                              << OP_CHECKMULTISIG,
+                    "New-CHECKMULTISIG 2-of-3 (110), last key garbage",
+                    newmultisigflags)
+            .Num(0b110)
+            .PushSigSchnorr(keys.key0)
+            .PushSigSchnorr(keys.key1));
+
     std::set<std::string> tests_set;
 
     {