diff --git a/SConstruct b/SConstruct
index 82a281190..30c1ed0a6 100644
--- a/SConstruct
+++ b/SConstruct
@@ -118,7 +118,7 @@ pretxncommit.style = python:style.check_whitespace
 """ % (ROOT)
         sys.exit(1)
 
-if ARGUMENTS['IGNORE_STYLE'] != 'True' and isdir(joinpath(ROOT, '.hg')):
+if ARGUMENTS.get('IGNORE_STYLE') != 'True' and isdir(joinpath(ROOT, '.hg')):
     try:
         from mercurial import ui
         check_style_hook(ui.ui())