diff --git a/taskcluster/ci/test/xpcshell.yml b/taskcluster/ci/test/xpcshell.yml
index fa1b0f92992d..9eded9a2eee2 100644
--- a/taskcluster/ci/test/xpcshell.yml
+++ b/taskcluster/ci/test/xpcshell.yml
@@ -12,6 +12,7 @@ job-defaults:
         by-test-platform:
             android-em-7.*: geckoview-androidTest.apk
             default: null
+    python-3: true
     mozharness:
         script:
             by-test-platform: