diff --git a/ext/mbstring/php_mbregex.c b/ext/mbstring/php_mbregex.c
index aa1eec16861..b6ed2b86e90 100644
--- a/ext/mbstring/php_mbregex.c
+++ b/ext/mbstring/php_mbregex.c
@@ -149,6 +149,7 @@ PHP_RSHUTDOWN_FUNCTION(mb_regex)
 		ZVAL_UNDEF(&MBREX(search_str));
 	}
 	MBREX(search_pos) = 0;
+	MBREX(search_re) = NULL;
 
 	if (MBREX(search_regs) != NULL) {
 		onig_region_free(MBREX(search_regs), 1);