diff --git a/xen/arch/x86/bitops.c b/xen/arch/x86/bitops.c
index 720ab32362..22cfb6d8ec 100644
--- a/xen/arch/x86/bitops.c
+++ b/xen/arch/x86/bitops.c
@@ -35,8 +35,8 @@ unsigned int __find_next_bit(
     if ( bit != 0 )
     {
         /* Look for a bit in the first word. */
-        set = __scanbit(*p >> bit, BITS_PER_LONG - bit);
-        if ( set < (BITS_PER_LONG - bit) )
+        set = __scanbit(*p >> bit, BITS_PER_LONG);
+        if ( set < BITS_PER_LONG )
             return (offset + set);
         offset += BITS_PER_LONG - bit;
         p++;
@@ -85,8 +85,8 @@ unsigned int __find_next_zero_bit(
     if ( bit != 0 )
     {
         /* Look for zero in the first word. */
-        set = __scanbit(~(*p >> bit), BITS_PER_LONG - bit);
-        if ( set < (BITS_PER_LONG - bit) )
+        set = __scanbit(~*p >> bit, BITS_PER_LONG);
+        if ( set < BITS_PER_LONG )
             return (offset + set);
         offset += BITS_PER_LONG - bit;
         p++;