diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index 182e4fbcb043c468b76980f34da22bede0cd2495..0f9052ec26f4c63d83717966b9abf3c5b0a2bd64 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -1420,7 +1420,7 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
         out_samples += 256 * s->out_channels;
     }
     *data_size = s->num_blocks * 256 * avctx->channels * sizeof (int16_t);
-    return s->frame_size;
+    return FFMIN(buf_size, s->frame_size);
 }
 
 /**