diff --git a/loopy/codegen/loop.py b/loopy/codegen/loop.py
index 171b10e198f978854dd5cabef6aa380751c255da..1a7d318bb66e5f392b9cd2b1cfc7f309278b5835 100644
--- a/loopy/codegen/loop.py
+++ b/loopy/codegen/loop.py
@@ -220,7 +220,7 @@ def intersect_kernel_with_slab(kernel, slab, iname):
 
     domch = DomainChanger(kernel, (iname,))
     orig_domain = domch.get_original_domain()
-    orig_domain, slab = isl.align_two(orig_domain, slab)
+    orig_domain, slab = isl.align_two(slab, orig_domain)
     return domch.get_kernel_with(orig_domain & slab)