diff --git a/loopy/transform/iname.py b/loopy/transform/iname.py
index c35b5064365293ac78cdd01af537c9d28bd67193..241b1d975de21b92677709278a872b0a20befe16 100644
--- a/loopy/transform/iname.py
+++ b/loopy/transform/iname.py
@@ -1198,7 +1198,8 @@ class _ReductionSplitter(RuleAwareIdentityMapper):
                 return Reduction(expr.operation, tuple(self.inames),
                         Reduction(expr.operation, tuple(leftover_inames),
                             self.rec(expr.expr, expn_state),
-                            expr.allow_simultaneous))
+                            expr.allow_simultaneous),
+                        expr.allow_simultaneous)
             else:
                 assert False
         else: