diff --git a/.github/workflows/deploy-book.yml b/.github/workflows/deploy-book.yml
index c1983ea..d41f3ea 100644
--- a/.github/workflows/deploy-book.yml
+++ b/.github/workflows/deploy-book.yml
@@ -14,7 +14,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: '3.x'
+        python-version: '3.9'
 
     - name: Install dependencies
       run: |