diff --git a/Dockerfile b/Dockerfile
index b2d4b91..88271f4 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,7 +3,8 @@
 FROM focs.ji.sjtu.edu.cn:5000/gitea/runner-images:ubuntu-latest
 
 # install joint-teapot
-RUN pip install git+https://mirror.ghproxy.com/https://github.com/BoYanZh/Joint-Teapot
+RUN pip install --no-cache-dir --upgrade pip && \
+    pip install --no-cache-dir git+https://mirror.ghproxy.com/https://github.com/BoYanZh/Joint-Teapot
 
 # install joj3 binary
 COPY bin/joj3 /usr/local/bin/