diff --git a/bin/convert_format.py b/bin/convert_format.py
index c222d95..e1f6a90 100644
--- a/bin/convert_format.py
+++ b/bin/convert_format.py
@@ -3,7 +3,7 @@
 
 """
 Usage:
-python -p MAC-Dev \
+python -p mac-dev \
     -s data/mac/dev/zh zh \
     -t data/mac/dev/en en \
     -a data/mac/dev/auto \