diff --git a/ext/standard/file.c b/ext/standard/file.c
index 4e136bedf5fab..40941bf024409 100644
--- a/ext/standard/file.c
+++ b/ext/standard/file.c
@@ -181,6 +181,12 @@ PHP_MSHUTDOWN_FUNCTION(file) /* {{{ */
 }
 /* }}} */
 
+static inline bool php_is_valid_flock_flag(zend_long s) {
+	const zend_long sb = s & ~PHP_LOCK_NB;
+	return (sb == PHP_LOCK_UN || sb == PHP_LOCK_SH ||
+		sb == PHP_LOCK_EX);
+}
+
 PHPAPI void php_flock_common(php_stream *stream, zend_long operation,
 	uint32_t operation_arg_num, zval *wouldblock, zval *return_value)
 {
@@ -188,7 +194,7 @@ PHPAPI void php_flock_common(php_stream *stream, zend_long operation,
 	int act;
 
 	act = operation & PHP_LOCK_UN;
-	if (act < 1 || act > 3) {
+	if (!php_is_valid_flock_flag(operation)) {
 		zend_argument_value_error(operation_arg_num, "must be one of LOCK_SH, LOCK_EX, or LOCK_UN");
 		RETURN_THROWS();
 	}
diff --git a/ext/standard/tests/file/flock.phpt b/ext/standard/tests/file/flock.phpt
index a3c1804584023..16609fb5d9939 100644
--- a/ext/standard/tests/file/flock.phpt
+++ b/ext/standard/tests/file/flock.phpt
@@ -31,7 +31,11 @@ var_dump($would);
 var_dump(flock($fp, LOCK_UN, $would));
 var_dump($would);
 
-var_dump(flock($fp, -1));
+try {
+    var_dump(flock($fp, -1));
+} catch (\ValueError $e) {
+    echo $e->getMessage() . \PHP_EOL;
+}
 
 try {
     var_dump(flock($fp, 0));
@@ -59,5 +63,5 @@ bool(true)
 int(0)
 bool(true)
 int(0)
-bool(true)
+flock(): Argument #2 ($operation) must be one of LOCK_SH, LOCK_EX, or LOCK_UN
 flock(): Argument #2 ($operation) must be one of LOCK_SH, LOCK_EX, or LOCK_UN