diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cfbfe30b3..89ca1c5b1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,6 +33,7 @@ jobs:
                 sudo apt install octave
 
                 CONDA_ENVIRONMENT=.test-conda-env-py3.yml
+                export MPLBACKEND=Agg
                 curl -L -O -k https://gitlab.tiker.net/inducer/ci-support/raw/master/build-and-test-py-project-within-miniconda.sh
                 . ./build-and-test-py-project-within-miniconda.sh
 
@@ -74,6 +75,7 @@ jobs:
         -   uses: actions/checkout@v2
         -   name: "Main Script"
             run: |
+                export MPLBACKEND=Agg
                 CONDA_ENVIRONMENT=.test-conda-env-py3.yml
                 USE_CONDA_BUILD=1
                 curl -L -O -k https://gitlab.tiker.net/inducer/ci-support/raw/master/build-py-project-and-run-examples.sh