diff --git a/.github/workflows/complement_tests.yml b/.github/workflows/complement_tests.yml
index 41b7be6192..31b65611d8 100644
--- a/.github/workflows/complement_tests.yml
+++ b/.github/workflows/complement_tests.yml
@@ -37,6 +37,10 @@ jobs:
           - arrangement: workers
             database: Postgres
 
+          - arrangement: workers
+            database: Postgres
+            mas: true
+
     steps:
       - name: Checkout synapse codebase
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
@@ -103,6 +107,7 @@ jobs:
         env:
           POSTGRES: ${{ (matrix.database == 'Postgres') && 1 || '' }}
           WORKERS: ${{ (matrix.arrangement == 'workers') && 1 || '' }}
+          MAS: ${{ (matrix.mas == true) && 1 || '' }}
 
       - name: Formatted sanity check Complement test logs
         # Always run this step if we attempted to run the Complement tests.
@@ -132,6 +137,7 @@ jobs:
         env:
           POSTGRES: ${{ (matrix.database == 'Postgres') && 1 || '' }}
           WORKERS: ${{ (matrix.arrangement == 'workers') && 1 || '' }}
+          MAS: ${{ (matrix.mas == true) && 1 || '' }}
           TEST_ONLY_IGNORE_POETRY_LOCKFILE: ${{ inputs.use_latest_deps && 1 || '' }}
           TEST_ONLY_SKIP_DEP_HASH_VERIFICATION: ${{ inputs.use_twisted_trunk  && 1 || '' }}
 
@@ -162,6 +168,7 @@ jobs:
         env:
           POSTGRES: ${{ (matrix.database == 'Postgres') && 1 || '' }}
           WORKERS: ${{ (matrix.arrangement == 'workers') && 1 || '' }}
+          MAS: ${{ (matrix.mas == true) && 1 || '' }}
           TEST_ONLY_IGNORE_POETRY_LOCKFILE: ${{ inputs.use_latest_deps && 1 || '' }}
           TEST_ONLY_SKIP_DEP_HASH_VERIFICATION: ${{ inputs.use_twisted_trunk  && 1 || '' }}