diff --git a/src/test/monolith_opcodes_tests.cpp b/src/test/monolith_opcodes_tests.cpp
--- a/src/test/monolith_opcodes_tests.cpp
+++ b/src/test/monolith_opcodes_tests.cpp
@@ -19,20 +19,24 @@
 std::array<uint32_t, 3> flagset{
     {0, STANDARD_SCRIPT_VERIFY_FLAGS, MANDATORY_SCRIPT_VERIFY_FLAGS}};
 
+static void CheckTestResult(uint32_t flags, const stacktype &original_stack,
+                            const CScript &script, const stacktype &expected) {
+    BaseSignatureChecker sigchecker;
+    ScriptError err = SCRIPT_ERR_OK;
+    stacktype stack{original_stack};
+    bool r = EvalScript(stack, script, flags, sigchecker, &err);
+    BOOST_CHECK(r);
+    BOOST_CHECK(stack == expected);
+}
+
 /**
  * General utility functions to check for script passing/failing.
  */
 static void CheckTestResultForAllFlags(const stacktype &original_stack,
                                        const CScript &script,
                                        const stacktype &expected) {
-    BaseSignatureChecker sigchecker;
-
     for (uint32_t flags : flagset) {
-        ScriptError err = SCRIPT_ERR_OK;
-        stacktype stack{original_stack};
-        bool r = EvalScript(stack, script, flags, sigchecker, &err);
-        BOOST_CHECK(r);
-        BOOST_CHECK(stack == expected);
+        CheckTestResult(flags, original_stack, script, expected);
     }
 }
 
@@ -627,6 +631,14 @@
 
     CheckNum2BinError({{}, {0x09, 0x02}}, SCRIPT_ERR_PUSH_SIZE);
 
+    // NUM2BIN can't take negative sizes, for which it throws an error
+    // "Push value size limit exceeded"
+    CheckNum2BinError({{}, {0x81}}, SCRIPT_ERR_PUSH_SIZE);
+    // ... except for negative zero of course (without minimaldata flag)
+    CheckTestResult(0, {{0x00, 0x80}, {0x80}}, CScript() << OP_NUM2BIN, {{}});
+    CheckTestResult(0, {{0x00, 0x80}, {0x00, 0x80}}, CScript() << OP_NUM2BIN,
+                    {{}});
+
     // Check that the requested encoding is possible.
     CheckNum2BinError({{0xab, 0xcd, 0xef, 0x80}, {0x03}},
                       SCRIPT_ERR_IMPOSSIBLE_ENCODING);