diff --git a/src/core_write.cpp b/src/core_write.cpp
--- a/src/core_write.cpp
+++ b/src/core_write.cpp
@@ -35,7 +35,7 @@
                 continue;
             }
 
-            if (op >= OP_NOP && op <= OP_NOP10) {
+            if (op >= OP_NOP && op < FIRST_UNDEFINED_OP_VALUE) {
                 std::string str(GetOpName(op));
                 if (str.substr(0, 3) == std::string("OP_")) {
                     ret += str.substr(3, std::string::npos) + " ";
@@ -222,7 +222,7 @@
 
         UniValue outValue(UniValue::VNUM, FormatMoney(txout.nValue));
         out.pushKV("value", outValue);
-        out.pushKV("n", (int64_t)i);
+        out.pushKV("n", int64_t(i));
 
         UniValue o(UniValue::VOBJ);
         ScriptPubKeyToUniv(txout.scriptPubKey, o, true);
diff --git a/src/test/core_io_tests.cpp b/src/test/core_io_tests.cpp
--- a/src/test/core_io_tests.cpp
+++ b/src/test/core_io_tests.cpp
@@ -145,4 +145,14 @@
                       std::runtime_error);
 }
 
+void TestFormatRoundTrip(const std::string &script) {
+    BOOST_CHECK_EQUAL(script, FormatScript(ParseScript(script)));
+}
+
+BOOST_AUTO_TEST_CASE(format_script_test) {
+    TestFormatRoundTrip("0 1 5 CHECKDATASIG CHECKSIG XOR NOP5 NOP10 "
+                        "CHECKDATASIGVERIFY DEPTH RETURN VERIFY SPLIT INVERT "
+                        "EQUAL HASH256 GREATERTHANOREQUAL RSHIFT");
+}
+
 BOOST_AUTO_TEST_SUITE_END()