diff --git a/.github/workflows/gramps-ci.yml b/.github/workflows/gramps-ci.yml
index e187eba6f..d3a92b778 100644
--- a/.github/workflows/gramps-ci.yml
+++ b/.github/workflows/gramps-ci.yml
@@ -68,6 +68,7 @@ jobs:
         python3 setup.py build
     - name: Run unit test suite
       run: |
+        export GDK_BACKEND=-
         python3 setup.py test
     - name: Trailing whitespace check
       run: |