diff --git a/lib/tools/ensure_dirs.py b/lib/tools/ensure_dirs.py
index 868e36cd57fa64f5fd8b678a8220e81be0fdc7c8..4c4e7a171deb085ab5b82ea1eb0a1b6b8e1b969c 100644
--- a/lib/tools/ensure_dirs.py
+++ b/lib/tools/ensure_dirs.py
@@ -224,7 +224,7 @@ def ParseOptions():
   """
   program = os.path.basename(sys.argv[0])
 
-  parser = optparse.OptionParser(usage="%%prog [--full-run]",
+  parser = optparse.OptionParser(usage="%prog [--full-run]",
                                  prog=program)
   parser.add_option(cli.DEBUG_OPT)
   parser.add_option(cli.VERBOSE_OPT)