Fix typo
diff --git a/Tools/msi/msi.py b/Tools/msi/msi.py
index 52dfa22..9f9d10a 100644
--- a/Tools/msi/msi.py
+++ b/Tools/msi/msi.py
@@ -361,7 +361,7 @@
     # See "Custom Action Type 1"
     if msilib.Win64:
         CheckDir = "CheckDir"
-        UpdateEditIdle = "UpdateEditIDLE"
+        UpdateEditIDLE = "UpdateEditIDLE"
     else:
         CheckDir =  "_CheckDir@4"
         UpdateEditIDLE = "_UpdateEditIDLE@4"