diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index 2c4ed49c12..70ae8099e9 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -722,6 +722,8 @@ static int rm_assemble_video_frame(AVFormatContext *s, AVIOContext *pb,
 
     if(++vst->cur_slice > vst->slices)
         return 1;
+    if(!vst->pkt.data)
+        return AVERROR(ENOMEM);
     AV_WL32(vst->pkt.data - 7 + 8*vst->cur_slice, 1);
     AV_WL32(vst->pkt.data - 3 + 8*vst->cur_slice, vst->videobufpos - 8*vst->slices - 1);
     if(vst->videobufpos + len > vst->videobufsize)