diff --git a/gerber/excellon_tool.py b/gerber/excellon_tool.py
index b7d67d4..31d72d5 100644
--- a/gerber/excellon_tool.py
+++ b/gerber/excellon_tool.py
@@ -60,7 +60,7 @@ class ExcellonToolDefinitionParser(object):
     matchers = [
                 (allegro_tool, 'mils'),
                 (allegro_comment_mils, 'mils'),
-                (allegro_comment_mils, 'mm'),
+                (allegro_comment_mm, 'mm'),
                 ]
     
     def __init__(self, settings=None):