diff --git a/.github/workflows/manual.yml b/.github/workflows/manual.yml
index f5af719..f0ad7ce 100644
--- a/.github/workflows/manual.yml
+++ b/.github/workflows/manual.yml
@@ -19,7 +19,7 @@ jobs:
         uses: actions/checkout@v2.3.4
        
       - name: Prepare
-        run: sudo apt-get install zfsutils-linux && sudo pip3 install coverage unittest2 mock
+        run: sudo apt-get install zfsutils-linux && sudo pip3 install coverage unittest2 mock==3.0.5
        
        
       - name: Regression test