diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index e39330580c5500764975cc33a36ad1e371148faa..f88eb3d4042051c3e12aac60dcbd49171e3376d1 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -881,7 +881,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 		return -EINVAL;
 	if (!unmap->size || unmap->size & mask)
 		return -EINVAL;
-	if (unmap->iova + unmap->size < unmap->iova ||
+	if (unmap->iova + unmap->size - 1 < unmap->iova ||
 	    unmap->size > SIZE_MAX)
 		return -EINVAL;