diff --git a/loopy/preprocess.py b/loopy/preprocess.py
index 229c6b7caafb17c309746edefffff88019ef4f50..00b05306b5f6f6a17e294a7019623cea444ad6cf 100644
--- a/loopy/preprocess.py
+++ b/loopy/preprocess.py
@@ -1247,6 +1247,8 @@ def realize_reduction(kernel, insn_id_filter=None, unknown_types_ok=True,
         prev_id = transfer_id
         bound = size
 
+        stage_exec_iname = None
+
         istage = 0
         while cur_size > 1: