diff --git a/test/test_loopy.py b/test/test_loopy.py
index 7957fc9cad3e55d295956df5efbe0ee1159ce319..6d98f93a9a84f29e2e7d2ca206892666f2dc8d31 100644
--- a/test/test_loopy.py
+++ b/test/test_loopy.py
@@ -1620,7 +1620,8 @@ def test_slab_decomposition_does_not_double_execute(ctx_factory):
 
     knl = lp.make_kernel(ctx.devices[0],
         "{ [i]: 0<=i<n }",
-        "a[i] = 2*a[i]")
+        "a[i] = 2*a[i]",
+        assumptions="n>=1")
 
     ref_knl = knl