diff --git a/src/_imaging.c b/src/_imaging.c
index 2a73a06338d..96c781abdc6 100644
--- a/src/_imaging.c
+++ b/src/_imaging.c
@@ -3767,9 +3767,9 @@ _compare_pixels(
         // These modes have three channels in four bytes,
         // so we have to ignore the last byte.
 #ifdef WORDS_BIGENDIAN
-        mask = 0xffffff00;
+        mask = 0xffff0000;
 #else
-        mask = 0x00ffffff;
+        mask = 0x0000ffff;
 #endif
     } else if (!strcmp(mode, "LA") || !strcmp(mode, "La") || !strcmp(mode, "PA")) {
         // These modes have two channels in four bytes,