diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 2a5c05ca7fca..2ab87e3f07e6 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2555,7 +2555,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
 			bus_addr  = address + s->dma_address + (j << PAGE_SHIFT);
 			iommu_unmap_page(domain, bus_addr, PAGE_SIZE);
 
-			if (--mapped_pages)
+			if (--mapped_pages == 0)
 				goto out_free_iova;
 		}
 	}