diff --git a/libavcodec/4xm.c b/libavcodec/4xm.c
index 6038e830a8..94cfb82668 100644
--- a/libavcodec/4xm.c
+++ b/libavcodec/4xm.c
@@ -829,7 +829,7 @@ static int decode_frame(AVCodecContext *avctx,
 
     if(frame_4cc == AV_RL32("ifr2")){
         p->pict_type= AV_PICTURE_TYPE_I;
-        if(decode_i2_frame(f, buf-4, frame_size) < 0){
+        if(decode_i2_frame(f, buf-4, frame_size+4) < 0){
             av_log(f->avctx, AV_LOG_ERROR, "decode i2 frame failed\n");
             return -1;
         }