diff --git a/third_party/libtiff/tif_getimage.c b/third_party/libtiff/tif_getimage.c
index 1cf6ac6b4..2861cdd1e 100644
--- a/third_party/libtiff/tif_getimage.c
+++ b/third_party/libtiff/tif_getimage.c
@@ -1281,7 +1281,7 @@ DECLAREContigPutFunc(putagreytile)
     while (h-- > 0) {
        for (x = w; x-- > 0;)
         {
-            *cp++ = BWmap[*pp][0] & (*(pp+1) << 24 | ~A1);
+            *cp++ = BWmap[*pp][0] & ((uint32)*(pp+1) << 24 | ~A1);
             pp += samplesperpixel;
         }
        cp += toskew;