diff --git a/docs/requirements.txt b/docs/requirements.txt
index db6c80998..30622230b 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==2.13.3
 webrtcvad
 websockets