diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8787aed..f4e7ac3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -80,5 +80,21 @@ jobs:
       - name: Composer update
         run: composer update
 
-      - name: Run PHPUnit
+      # "master" currently tracks MW >= 1.46, where tests/phpunit/phpunit.php
+      # was removed. Once REL1_46 lands in the matrix, it needs the master
+      # invocation below as well.
+      - name: Run PHPUnit (MW < master)
+        if: matrix.mw != 'master'
         run: php tests/phpunit/phpunit.php -c extensions/Bootstrap/
+
+      - name: Run PHPUnit (MW master)
+        if: matrix.mw == 'master'
+        run: |
+          # TODO: phpunit.xml.template is export-ignored from GitHub's tarball
+          # archive, so we fetch it separately. Remove this once installWiki.sh
+          # switches to `git clone`, or MW drops the export-ignore.
+          if [ ! -f phpunit.xml.template ]; then
+            wget -q -O phpunit.xml.template "https://raw.githubusercontent.com/wikimedia/mediawiki/${{ matrix.mw }}/phpunit.xml.template"
+          fi
+          composer phpunit:config
+          vendor/bin/phpunit --group extension-bootstrap