diff --git a/Lib/encodings/aliases.py b/Lib/encodings/aliases.py
index c842c610a7f..b4212f2acff 100644
--- a/Lib/encodings/aliases.py
+++ b/Lib/encodings/aliases.py
@@ -27,7 +27,7 @@
     '646'                : 'ascii',
     'ansi_x3.4_1968'     : 'ascii',
     'ansi_x3.4_1986'     : 'ascii',
-    'ansi-x3-4-1968'     : 'ascii',
+    'ansi_x3_4_1968'     : 'ascii',
     'cp367'              : 'ascii',
     'csascii'            : 'ascii',
     'ibm367'             : 'ascii',