diff --git a/lib/iommu-helper.c b/lib/iommu-helper.c
index c27e269210c4..a816f3a80625 100644
--- a/lib/iommu-helper.c
+++ b/lib/iommu-helper.c
@@ -29,8 +29,7 @@ unsigned long iommu_area_alloc(unsigned long *map, unsigned long size,
 	index = bitmap_find_next_zero_area(map, size, start, nr, align_mask);
 	if (index < size) {
 		if (iommu_is_span_boundary(index, nr, shift, boundary_size)) {
-			/* we could do more effectively */
-			start = index + 1;
+			start = ALIGN(shift + index, boundary_size) - shift;
 			goto again;
 		}
 		bitmap_set(map, index, nr);