diff --git a/include/asm-generic/word-at-a-time.h b/include/asm-generic/word-at-a-time.h
index d3909ef..d96deb4 100644
--- a/include/asm-generic/word-at-a-time.h
+++ b/include/asm-generic/word-at-a-time.h
@@ -50,11 +50,7 @@
 }
 
 #ifndef zero_bytemask
-#ifdef CONFIG_64BIT
-#define zero_bytemask(mask)	(~0ul << fls64(mask))
-#else
-#define zero_bytemask(mask)	(~0ul << fls(mask))
-#endif /* CONFIG_64BIT */
-#endif /* zero_bytemask */
+#define zero_bytemask(mask) (~0ul << __fls(mask) << 1)
+#endif
 
 #endif /* _ASM_WORD_AT_A_TIME_H */