diff --git a/Lib/re.py b/Lib/re.py
index a7865932128..efc1ded1083 100644
--- a/Lib/re.py
+++ b/Lib/re.py
@@ -16,5 +16,7 @@
 # thanks /F
 #
 
+engine = "sre" # Some apps might use this undocumented variable
+
 from sre import *
 from sre import __all__