diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 44b1231157..719ce19ab3 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -3379,12 +3379,12 @@ static void vtd_address_space_unmap(VTDAddressSpace *as, IOMMUNotifier *n)
      * VT-d spec), otherwise we need to consider overflow of 64 bits.
      */
 
-    if (end > VTD_ADDRESS_SIZE(s->aw_bits)) {
+    if (end > VTD_ADDRESS_SIZE(s->aw_bits) - 1) {
         /*
          * Don't need to unmap regions that is bigger than the whole
          * VT-d supported address space size
          */
-        end = VTD_ADDRESS_SIZE(s->aw_bits);
+        end = VTD_ADDRESS_SIZE(s->aw_bits) - 1;
     }
 
     assert(start <= end);