diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 305908700b..61857d0e5c 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -787,7 +787,7 @@ static int decode_trns_chunk(AVCodecContext *avctx, PNGDecContext *s,
 
         for (i = 0; i < length / 2; i++) {
             /* only use the least significant bits */
-            v = bytestream2_get_be16(&s->gb) & ((1 << s->bit_depth) - 1);
+            v = av_mod_uintp2(bytestream2_get_be16(&s->gb), s->bit_depth);
 
             if (s->bit_depth > 8)
                 AV_WB16(&s->transparent_color_be[2 * i], v);