diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index d4857faf8a..dc336c239a 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -48,17 +48,17 @@ static unsigned long *monitor_bitmap_for_msr(const struct domain *d, u32 *msr)
 
     switch ( *msr )
     {
-    case 0 ... 0x1fff:
+    case 0 ... 0x1fffU:
         BUILD_BUG_ON(sizeof(d->arch.monitor.msr_bitmap->low) * 8 <= 0x1fff);
         return d->arch.monitor.msr_bitmap->low;
 
-    case 0x40000000 ... 0x40001fff:
+    case 0x40000000U ... 0x40001fffU:
         BUILD_BUG_ON(
             sizeof(d->arch.monitor.msr_bitmap->hypervisor) * 8 <= 0x1fff);
         *msr &= 0x1fff;
         return d->arch.monitor.msr_bitmap->hypervisor;
 
-    case 0xc0000000 ... 0xc0001fff:
+    case 0xc0000000U ... 0xc0001fffU:
         BUILD_BUG_ON(sizeof(d->arch.monitor.msr_bitmap->high) * 8 <= 0x1fff);
         *msr &= 0x1fff;
         return d->arch.monitor.msr_bitmap->high;