diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1313,6 +1313,21 @@
                             // Disabled opcodes.
                             return set_error(serror, SCRIPT_ERR_DISABLED_OPCODE);
                         }
+                        // (in -- out)
+                        if (stack.size() < 1) {
+                            return set_error(
+                                serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
+                        }
+                        valtype bin = stacktop(-1);
+                        // big endian to little endian conversion
+                        std::reverse(bin.begin(), bin.end());
+                        CScriptNum num(bin, false);
+                        if (num > (INT_MAX >> 1) || num < (INT_MIN >> 1)) {
+                            return set_error(
+                                serror, SCRIPT_ERR_INVALID_BIN2NUM_OPERATION);
+                        }
+                        stack.pop_back();
+                        stack.push_back(num.getvch());
                     } break;
 
                     case OP_NUM2BIN: {