diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 40157b3..984498f 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -21,9 +21,13 @@ jobs:
       run: |
         python --version
     - name: Install Python package
+      env:
+        PYTHONWARNINGS: error,default::DeprecationWarning
       run: |
         $PIP install .
     - name: Install docs dependencies
+      env:
+        PYTHONWARNINGS: error,default::DeprecationWarning
       run: |
         $PIP install -r doc/requirements.txt
     - name: Build HTML