diff --git a/loopy/symbolic.py b/loopy/symbolic.py
index fe7b458d8469c5c6a1a3c09470e34c43c5cd1e7a..015d29a7a4effa8f1965c1f3fcce88681b037447 100644
--- a/loopy/symbolic.py
+++ b/loopy/symbolic.py
@@ -396,7 +396,7 @@ class ExpandingIdentityMapper(IdentityMapper):
 
     def __call__(self, expr, insn_id):
         if insn_id is not None:
-            stack = (insn_id,)
+            stack = ((insn_id, None),)
         else:
             stack = ()