diff --git a/libavformat/oggparsedaala.c b/libavformat/oggparsedaala.c
index 24567f93a9..3651ca188b 100644
--- a/libavformat/oggparsedaala.c
+++ b/libavformat/oggparsedaala.c
@@ -123,7 +123,12 @@ static int daala_header(AVFormatContext *s, int idx)
 
         hdr->frame_duration = bytestream2_get_ne32(&gb);
         hdr->gpshift = bytestream2_get_byte(&gb);
-        hdr->gpmask  = (1 << hdr->gpshift) - 1;
+        if (hdr->gpshift >= 32) {
+            av_log(s, AV_LOG_ERROR, "Too large gpshift %d (>= 32).\n",
+                   hdr->gpshift);
+            return AVERROR_INVALIDDATA;
+        }
+        hdr->gpmask  = (1U << hdr->gpshift) - 1;
 
         hdr->format.depth  = 8 + 2*(bytestream2_get_byte(&gb)-1);
 
diff --git a/libavformat/oggparsetheora.c b/libavformat/oggparsetheora.c
index 6e6a362e1e..5f057c3c8a 100644
--- a/libavformat/oggparsetheora.c
+++ b/libavformat/oggparsetheora.c
@@ -108,7 +108,7 @@ static int theora_header(AVFormatContext *s, int idx)
             skip_bits(&gb, 2);
 
         thp->gpshift = get_bits(&gb, 5);
-        thp->gpmask  = (1 << thp->gpshift) - 1;
+        thp->gpmask  = (1U << thp->gpshift) - 1;
 
         st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
         st->codec->codec_id   = AV_CODEC_ID_THEORA;