diff --git a/docs/requirements.txt b/docs/requirements.txt
index c2d56bf9..e4020422 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -38,7 +38,7 @@ sphinx-markdown-tables
 sphinx_rtd_theme
 textgrid
 timer
-ToJyutping
+ToJyutping==0.2.1
 typeguard
 webrtcvad
 websockets