diff --git a/Lib/tkinter/Tkconstants.py b/Lib/tkinter/Tkconstants.py
index 9612da9..dd4fb0e 100755
--- a/Lib/tkinter/Tkconstants.py
+++ b/Lib/tkinter/Tkconstants.py
@@ -68,3 +68,9 @@
 COMMAND='command'
 RADIOBUTTON='radiobutton'
 SEPARATOR='separator'
+
+# Selection modes for list boxes
+SINGLE='single'
+BROWSE='browse'
+MULTIPLE='multiple'
+EXTENDED='extended'