diff --git a/Dockerfile b/Dockerfile
index 2c9ff66..bee1836 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -15,6 +15,7 @@ RUN sed -i s@/deb.debian.org/@/mirrors.tuna.tsinghua.edu.cn/@g /etc/apt/sources.
 
 # install joint-teapot && joj3-forge
 RUN pip install --no-cache-dir --break-system-packages \
+    --index-url https://pypi.tuna.tsinghua.edu.cn/simple \
     git+https://focs.ji.sjtu.edu.cn/git/JOJ/Joint-Teapot \
     git+https://focs.ji.sjtu.edu.cn/git/JOJ/JOJ3-config-generator