diff --git a/ffmpeg.c b/ffmpeg.c
index 40d929dac2316e19ac6329de501b18734baf1144..f5029987ade2e025d472ceb614990b4d2927744e 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -1178,6 +1178,8 @@ static void do_video_out(AVFormatContext *s,
     av_frame_unref(ost->last_frame);
     if (next_picture)
         av_frame_ref(ost->last_frame, next_picture);
+    else
+        av_frame_free(&ost->last_frame);
 }
 
 static double psnr(double d)