diff --git a/Zend/tests/enum/json_encode.phpt b/Zend/tests/enum/json_encode.phpt
index 12ed0d3d445..f1174db7ae8 100644
--- a/Zend/tests/enum/json_encode.phpt
+++ b/Zend/tests/enum/json_encode.phpt
@@ -26,6 +26,10 @@ enum CustomFoo implements JsonSerializable {
 function test($value) {
     var_dump(json_encode($value));
     echo json_last_error_msg() . "\n";
+    if (json_last_error() !== JSON_ERROR_NONE) {
+        echo json_last_error() . ' === '  . JSON_ERROR_NON_BACKED_ENUM . ":\n";
+        var_dump(json_last_error() === JSON_ERROR_NON_BACKED_ENUM);
+    }
 
     try {
         var_dump(json_encode($value, JSON_THROW_ON_ERROR));
@@ -44,6 +48,8 @@ test(CustomFoo::Bar);
 --EXPECT--
 bool(false)
 Non-backed enums have no default serialization
+11 === 11:
+bool(true)
 JsonException: Non-backed enums have no default serialization
 string(1) "0"
 No error
diff --git a/ext/json/json.c b/ext/json/json.c
index b21ed4d14b2..c66a48c49ea 100644
--- a/ext/json/json.c
+++ b/ext/json/json.c
@@ -83,6 +83,7 @@ static PHP_MINIT_FUNCTION(json)
 	PHP_JSON_REGISTER_CONSTANT("JSON_ERROR_UNSUPPORTED_TYPE", PHP_JSON_ERROR_UNSUPPORTED_TYPE);
 	PHP_JSON_REGISTER_CONSTANT("JSON_ERROR_INVALID_PROPERTY_NAME", PHP_JSON_ERROR_INVALID_PROPERTY_NAME);
 	PHP_JSON_REGISTER_CONSTANT("JSON_ERROR_UTF16", PHP_JSON_ERROR_UTF16);
+	PHP_JSON_REGISTER_CONSTANT("JSON_ERROR_NON_BACKED_ENUM", PHP_JSON_ERROR_NON_BACKED_ENUM);
 
 	return SUCCESS;
 }