diff --git a/build-python.sh b/build-python.sh
index 823de5b..d846a27 100755
--- a/build-python.sh
+++ b/build-python.sh
@@ -6,6 +6,8 @@
 #   $ sudo pip install futures
 #   $ sudo pip install enum
 #   $ sudo pip install concurrent
+# for protoc, please install protoc by:
+#   $ apt-get install protobuf-compiler
 
 python -m compileall .