diff --git a/libavfilter/defaults.c b/libavfilter/defaults.c
index 3484e0e6d5..85fdffba44 100644
--- a/libavfilter/defaults.c
+++ b/libavfilter/defaults.c
@@ -23,7 +23,7 @@
 #include "avfilter.h"
 
 /* TODO: buffer pool.  see comment for avfilter_default_get_video_buffer() */
-void avfilter_default_free_video_buffer(AVFilterPic *pic)
+static void avfilter_default_free_video_buffer(AVFilterPic *pic)
 {
     av_free(pic->data[0]);
     av_free(pic);