diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
index 8a4ec9b560..a8a3b76987 100644
--- a/libavformat/dashdec.c
+++ b/libavformat/dashdec.c
@@ -1156,6 +1156,7 @@ static int parse_manifest_adaptationset(AVFormatContext *s, const char *url,
 
 err:
     xmlFree(c->adaptionset_lang);
+    c->adaptionset_lang = NULL;
     return ret;
 }