diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
index 7247f14788..63ea2d0b1e 100644
--- a/include/qemu/bitmap.h
+++ b/include/qemu/bitmap.h
@@ -57,11 +57,8 @@
  * find_next_bit(addr, nbits, bit)	Position next set bit in *addr >= bit
  */
 
-#define BITMAP_LAST_WORD_MASK(nbits)                                    \
-    (                                                                   \
-        ((nbits) % BITS_PER_LONG) ?                                     \
-        (1UL<<((nbits) % BITS_PER_LONG))-1 : ~0UL                       \
-        )
+#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
+#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
 
 #define DECLARE_BITMAP(name,bits)                  \
         unsigned long name[BITS_TO_LONGS(bits)]
diff --git a/util/bitmap.c b/util/bitmap.c
index 40aadfb4f3..43ed011720 100644
--- a/util/bitmap.c
+++ b/util/bitmap.c
@@ -157,8 +157,6 @@ int slow_bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
     return result != 0;
 }
 
-#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))
-
 void bitmap_set(unsigned long *map, long start, long nr)
 {
     unsigned long *p = map + BIT_WORD(start);