diff --git a/libavcodec/mpegvideo_enc.c b/libavcodec/mpegvideo_enc.c
index c4c174a02e..5fab302148 100644
--- a/libavcodec/mpegvideo_enc.c
+++ b/libavcodec/mpegvideo_enc.c
@@ -1252,6 +1252,8 @@ static int load_input_picture(MpegEncContext *s, const AVFrame *pic_arg)
     /* shift buffer entries */
     for (int i = flush_offset; i <= MAX_B_FRAMES; i++)
         s->input_picture[i - flush_offset] = s->input_picture[i];
+    for (int i = MAX_B_FRAMES + 1 - flush_offset; i <= MAX_B_FRAMES; i++)
+        s->input_picture[i] = NULL;
 
     s->input_picture[encoding_delay] = pic;