Index: src/script/interpreter.cpp
===================================================================
--- src/script/interpreter.cpp
+++ src/script/interpreter.cpp
@@ -88,7 +88,7 @@
     if (fEnabledOpCodesMagnetic) {
         switch (opcode) {
             case OP_INVERT:
-                return true;
+                return false;
 
             case OP_2MUL:
                 return true;
@@ -1188,6 +1188,19 @@
                         }
                     } break;
 
+                    case OP_INVERT: {
+                        // (x -- out)
+                        if (stack.size() < 1) {
+                            return set_error(
+                                serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
+                        }
+
+                        valtype &x = stacktop(-1);
+                        for (size_t i = 0; i < x.size(); i++) {
+                            x[i] = ~x[i];
+                        }
+                    } break;
+
                     default:
                         return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
                 }
Index: src/test/data/script_tests.json
===================================================================
--- src/test/data/script_tests.json
+++ src/test/data/script_tests.json
@@ -928,8 +928,8 @@
 ["NOP", "SIZE 1", "P2SH,STRICTENC", "INVALID_STACK_OPERATION"],
 
 ["Disabled opcodes"],
-["'abc'", "IF INVERT ELSE 1 ENDIF", "P2SH,STRICTENC", "DISABLED_OPCODE", "INVERT disabled"],
-["'abc'", "IF INVERT ELSE 1 ENDIF", "P2SH,STRICTENC,MAGNETIC_OPCODES", "DISABLED_OPCODE", "INVERT disabled"],
+["'abc' 0", "IF INVERT ELSE 1 ENDIF", "P2SH,STRICTENC", "DISABLED_OPCODE", "INVERT disabled"],
+["'abc' 0", "IF INVERT ELSE 1 ENDIF", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT enabled"],
 ["2 0 IF 2MUL ELSE 1 ENDIF", "NOP", "P2SH,STRICTENC", "DISABLED_OPCODE", "2MUL disabled"],
 ["2 0 IF 2MUL ELSE 1 ENDIF", "NOP", "P2SH,STRICTENC,MAGNETIC_OPCODES", "DISABLED_OPCODE", "2MUL disabled"],
 ["2 0 IF 2DIV ELSE 1 ENDIF", "NOP", "P2SH,STRICTENC", "DISABLED_OPCODE", "2DIV disabled"],
@@ -952,6 +952,7 @@
 ["", "AND 0 EQUAL", "P2SH,STRICTENC", "INVALID_STACK_OPERATION", "AND, empty stack"],
 ["0 1", "AND 1 EQUAL", "P2SH,STRICTENC", "OPERAND_SIZE", "AND, different operand size"],
 ["0x01 0xab 0x01 0xcd", "AND 0x01 0x89 EQUAL", "P2SH,STRICTENC", "OK", "AND, more complex operands"],
+
 ["OR"],
 ["0 0", "OR 0 EQUAL", "P2SH,STRICTENC", "OK", "OR, empty parameters"],
 ["0x01 0x00 0x01 0x00", "OR 0x01 0x00 EQUAL", "P2SH,STRICTENC", "OK", "OR, simple and"],
@@ -962,6 +963,7 @@
 ["", "OR 0 EQUAL", "P2SH,STRICTENC", "INVALID_STACK_OPERATION", "OR, empty stack"],
 ["0 1", "OR 1 EQUAL", "P2SH,STRICTENC", "OPERAND_SIZE", "OR, different operand size"],
 ["0x01 0xab 0x01 0xcd", "OR 0x01 0xef EQUAL", "P2SH,STRICTENC", "OK", "XOR, more complex operands"],
+
 ["XOR"],
 ["0 0", "XOR 0 EQUAL", "P2SH,STRICTENC", "OK", "XOR, empty parameters"],
 ["0x01 0x00 0x01 0x00", "XOR 0x01 0x00 EQUAL", "P2SH,STRICTENC", "OK", "XOR, simple and"],
@@ -973,6 +975,19 @@
 ["0 1", "XOR 1 EQUAL", "P2SH,STRICTENC", "OPERAND_SIZE", "XOR, different operand size"],
 ["0x01 0xab 0x01 0xcd", "XOR 0x01 0x66 EQUAL", "P2SH,STRICTENC", "OK", "XOR, more complex operands"],
 
+["INVERT"],
+["", "INVERT", "P2SH,STRICTENC,MAGNETIC_OPCODES", "INVALID_STACK_OPERATION", "INVERT, invalid parameter count"],
+["0x0100", "INVERT 0x01FF EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, simple"],
+["0x01FF", "INVERT 0x0100 EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, simple"],
+["0x00", "INVERT 0x00 EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, empty"],
+["0x020F0F", "INVERT 0x02F0F0 EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, 2 bytes"],
+["0x03FF0000", "INVERT 0x0300FFFF EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, 3 bytes"],
+["0x0300FFFF", "INVERT 0x03FF0000 EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, 3 bytes"],
+["0x03FFFFFF", "INVERT 0x03000000 EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, 3 bytes"],
+["0x03801234", "INVERT 0x037FEDCB EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, 3 bytes"],
+["0x088012348012341234", "INVERT 0x087FEDCB7FEDCBEDCB EQUAL", "P2SH,STRICTENC,MAGNETIC_OPCODES", "OK", "INVERT, 8 bytes"],
+
+["Arithmetic opcodes"],
 ["DIV"],
 ["1 1", "DIV 1 EQUAL", "P2SH,STRICTENC", "OK"],
 ["1 -1", "DIV -1 EQUAL", "P2SH,STRICTENC", "OK"],
Index: src/test/opcode_tests.cpp
===================================================================
--- src/test/opcode_tests.cpp
+++ src/test/opcode_tests.cpp
@@ -30,7 +30,9 @@
     for (uint32_t flags : flagset) {
         ScriptError err = SCRIPT_ERR_OK;
         stacktype stack{original_stack};
-        bool r = EvalScript(stack, script, flags, sigchecker, &err);
+        bool r =
+            EvalScript(stack, script, flags | SCRIPT_ENABLE_MAGNETIC_OPCODES,
+                       sigchecker, &err);
         BOOST_CHECK(r);
         BOOST_CHECK(stack == expected);
     }
@@ -41,7 +43,8 @@
     BaseSignatureChecker sigchecker;
     ScriptError err = SCRIPT_ERR_OK;
     stacktype stack{original_stack};
-    bool r = EvalScript(stack, script, flags, sigchecker, &err);
+    bool r = EvalScript(stack, script, flags | SCRIPT_ENABLE_MAGNETIC_OPCODES,
+                        sigchecker, &err);
     BOOST_CHECK(!r);
     BOOST_CHECK_EQUAL(err, expected_error);
 }
@@ -71,6 +74,11 @@
     CheckTestResultForAllFlags({a, b}, CScript() << op, {expected});
 }
 
+static void CheckUnaryOp(const valtype &a, opcodetype op,
+                         const valtype &expected) {
+    CheckTestResultForAllFlags({a}, CScript() << op, {expected});
+}
+
 static valtype NegativeValtype(const valtype &v) {
     valtype r(v);
     if (r.size() > 0) {
@@ -392,6 +400,14 @@
     CheckAllBitwiseOpErrors({b, {}}, SCRIPT_ERR_INVALID_OPERAND_SIZE);
 }
 
+BOOST_AUTO_TEST_CASE(invert_test) {
+    CheckUnaryOp({}, OP_INVERT, {});
+    CheckUnaryOp({0x00}, OP_INVERT, {0xFF});
+    CheckUnaryOp({0xFF}, OP_INVERT, {0x00});
+    CheckUnaryOp({0xFF, 0xA0, 0xCE, 0xA0, 0x96, 0x12}, OP_INVERT,
+                 {0x00, 0x5F, 0x31, 0x5F, 0x69, 0xED});
+}
+
 /**
  * String opcodes.
  */