diff --git a/libavfilter/avfiltergraph.c b/libavfilter/avfiltergraph.c
index 5211c762e1..d4b6bf1b87 100644
--- a/libavfilter/avfiltergraph.c
+++ b/libavfilter/avfiltergraph.c
@@ -112,7 +112,8 @@ int avfilter_graph_load_chain(AVFilterGraph *graph,
 
 fail:
     destroy_graph_filters(graph);
-    *first = *last = NULL;
+    if(first) *first = NULL;
+    if(last)  *last  = NULL;
     return -1;
 }