diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index a0e9bbd5..d20ca8a7 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -31,6 +31,8 @@ jobs:
         if: startsWith(matrix.os, 'ubuntu')
         run: sudo apt-get install -y libsndfile1
       - name: Run tests
+        env:
+          MPLBACKEND: Agg
         run: uv run --with ${{ matrix.numpy }} --extra dev pytest
 
   test-deb11-i386: