diff --git a/main/frame.c b/main/frame.c
index 9c4d744d68..47b518c37f 100644
--- a/main/frame.c
+++ b/main/frame.c
@@ -797,6 +797,10 @@ int ast_parse_allow_disallow(struct ast_codec_pref *pref, struct ast_format_cap
 	char *parse = NULL, *this = NULL, *psize = NULL;
 	struct ast_format format;
 
+	if (!allowing && ast_strlen_zero(list)) {
+		return 0;
+	}
+
 	parse = ast_strdupa(list);
 	while ((this = strsep(&parse, ","))) {
 		iter_allowing = allowing;