diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c
index 1e7e0d697d..b22baccad5 100644
--- a/libavcodec/tiff.c
+++ b/libavcodec/tiff.c
@@ -327,7 +327,8 @@ static void unpack_gray(TiffContext *s, AVFrame *p,
     GetBitContext gb;
     uint16_t *dst = (uint16_t *)(p->data[0] + lnum * p->linesize[0]);
 
-    init_get_bits8(&gb, src, width);
+    int ret = init_get_bits8(&gb, src, width);
+    av_assert1(ret >= 0);
 
     for (int i = 0; i < s->width; i++) {
         dst[i] = get_bits(&gb, bpp);