diff --git a/src/script/script.h b/src/script/script.h
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -456,26 +456,16 @@
         READWRITEAS(CScriptBase, *this);
     }
 
-    CScript &operator+=(const CScript &b) {
-        reserve(size() + b.size());
-        insert(end(), b.begin(), b.end());
-        return *this;
-    }
-
-    friend CScript operator+(const CScript &a, const CScript &b) {
-        CScript ret = a;
-        ret += b;
-        return ret;
-    }
-
     explicit CScript(int64_t b) { operator<<(b); }
-
     explicit CScript(opcodetype b) { operator<<(b); }
     explicit CScript(const CScriptNum &b) { operator<<(b); }
     // delete non-existent constructor to defend against future introduction
     // e.g. via prevector
     explicit CScript(const std::vector<uint8_t> &b) = delete;
 
+    /** Delete non-existent operator to defend against future introduction */
+    CScript &operator<<(const CScript &b) = delete;
+
     CScript &operator<<(int64_t b) { return push_int64(b); }
 
     CScript &operator<<(opcodetype opcode) {
@@ -512,15 +502,6 @@
         return *this;
     }
 
-    CScript &operator<<(const CScript &b) {
-        // I'm not sure if this should push the script or concatenate scripts.
-        // If there's ever a use for pushing a script onto a script, delete this
-        // member fn.
-        assert(!"Warning: Pushing a CScript onto a CScript with << is probably "
-                "not intended, use + to concatenate!");
-        return *this;
-    }
-
     bool GetOp(const_iterator &pc, opcodetype &opcodeRet,
                std::vector<uint8_t> &vchRet) const {
         return GetScriptOp(pc, end(), opcodeRet, &vchRet);
diff --git a/src/test/fuzz/script_ops.cpp b/src/test/fuzz/script_ops.cpp
--- a/src/test/fuzz/script_ops.cpp
+++ b/src/test/fuzz/script_ops.cpp
@@ -16,12 +16,16 @@
     CScript script = ConsumeScript(fuzzed_data_provider);
     while (fuzzed_data_provider.remaining_bytes() > 0) {
         switch (fuzzed_data_provider.ConsumeIntegralInRange(0, 7)) {
-            case 0:
-                script += ConsumeScript(fuzzed_data_provider);
+            case 0: {
+                CScript s = ConsumeScript(fuzzed_data_provider);
+                script = std::move(s);
                 break;
-            case 1:
-                script = script + ConsumeScript(fuzzed_data_provider);
+            }
+            case 1: {
+                const CScript &s = ConsumeScript(fuzzed_data_provider);
+                script = s;
                 break;
+            }
             case 2:
                 script << fuzzed_data_provider.ConsumeIntegral<int64_t>();
                 break;
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
@@ -314,9 +314,9 @@
         return *this;
     }
 
-    TestBuilder &Add(const CScript &_script) {
+    TestBuilder &Opcode(const opcodetype &_op) {
         DoPush();
-        spendTx.vin[0].scriptSig += _script;
+        spendTx.vin[0].scriptSig << _op;
         return *this;
     }
 
@@ -1085,7 +1085,7 @@
                                 0)
                         .Num(0)
                         .PushSigECDSA(keys.key1)
-                        .Add(CScript() << OP_DUP));
+                        .Opcode(OP_DUP));
     tests.push_back(
         TestBuilder(
             CScript() << OP_2 << ToByteVector(keys.pubkey1C)
@@ -1095,7 +1095,7 @@
             SCRIPT_VERIFY_SIGPUSHONLY)
             .Num(0)
             .PushSigECDSA(keys.key1)
-            .Add(CScript() << OP_DUP)
+            .Opcode(OP_DUP)
             .SetScriptError(ScriptError::SIG_PUSHONLY));
     tests.push_back(
         TestBuilder(
@@ -1103,19 +1103,19 @@
             "P2SH(P2PK) with non-push scriptSig but no P2SH or SIGPUSHONLY", 0,
             true)
             .PushSigECDSA(keys.key2)
-            .Add(CScript() << OP_NOP8)
+            .Opcode(OP_NOP8)
             .PushRedeem());
     tests.push_back(
         TestBuilder(CScript() << ToByteVector(keys.pubkey2C) << OP_CHECKSIG,
                     "P2PK with non-push scriptSig but with P2SH validation", 0)
             .PushSigECDSA(keys.key2)
-            .Add(CScript() << OP_NOP8));
+            .Opcode(OP_NOP8));
     tests.push_back(
         TestBuilder(CScript() << ToByteVector(keys.pubkey2C) << OP_CHECKSIG,
                     "P2SH(P2PK) with non-push scriptSig but no SIGPUSHONLY",
                     SCRIPT_VERIFY_P2SH, true)
             .PushSigECDSA(keys.key2)
-            .Add(CScript() << OP_NOP8)
+            .Opcode(OP_NOP8)
             .PushRedeem()
             .SetScriptError(ScriptError::SIG_PUSHONLY));
     tests.push_back(
@@ -1123,7 +1123,7 @@
                     "P2SH(P2PK) with non-push scriptSig but not P2SH",
                     SCRIPT_VERIFY_SIGPUSHONLY, true)
             .PushSigECDSA(keys.key2)
-            .Add(CScript() << OP_NOP8)
+            .Opcode(OP_NOP8)
             .PushRedeem()
             .SetScriptError(ScriptError::SIG_PUSHONLY));
     tests.push_back(
@@ -3208,25 +3208,6 @@
     BOOST_CHECK(!script.HasValidOps());
 }
 
-BOOST_AUTO_TEST_CASE(script_can_append_self) {
-    CScript s, d;
-
-    s = ScriptFromHex("00");
-    s += s;
-    d = ScriptFromHex("0000");
-    BOOST_CHECK(s == d);
-
-    // check doubling a script that's large enough to require reallocation
-    static const char hex[] =
-        "04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6"
-        "bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f";
-    s = CScript() << ParseHex(hex) << OP_CHECKSIG;
-    d = CScript() << ParseHex(hex) << OP_CHECKSIG << ParseHex(hex)
-                  << OP_CHECKSIG;
-    s += s;
-    BOOST_CHECK(s == d);
-}
-
 #if defined(HAVE_CONSENSUS_LIB)
 
 /* Test simple (successful) usage of bitcoinconsensus_verify_script */