diff --git a/libavfilter/vf_pullup.c b/libavfilter/vf_pullup.c
index 73ffa68f8f..9b9064c649 100644
--- a/libavfilter/vf_pullup.c
+++ b/libavfilter/vf_pullup.c
@@ -137,7 +137,7 @@ static void free_field_queue(PullupField *head)
         av_free(f->combs);
         av_free(f->vars);
         next = f->next;
-        memset(f, 0, sizeof(*f));
+        memset(f, 0, sizeof(*f)); // clear all pointers to avoid stale ones
         av_free(f);
         f = next;
     } while (f != head);