diff --git a/ext/date/php_date.c b/ext/date/php_date.c
index bcfc9405a1e..5a1226a3929 100644
--- a/ext/date/php_date.c
+++ b/ext/date/php_date.c
@@ -1610,7 +1610,7 @@ PHP_FUNCTION(checkdate)
 		RETURN_FALSE;
 	}
 
-	if (y < 1 || y > 32767 || timelib_valid_date(y, m, d)) {
+	if (y < 1 || y > 32767 || !timelib_valid_date(y, m, d)) {
 		RETURN_FALSE;
 	}
 	RETURN_TRUE;	/* True : This month, day, year arguments are valid */