diff --git a/.github/workflows/modgc.yml b/.github/workflows/modgc.yml
index 5354d9bb97..1e64fd5109 100644
--- a/.github/workflows/modgc.yml
+++ b/.github/workflows/modgc.yml
@@ -26,8 +26,8 @@ jobs:
       matrix:
         gc:
           - name: default
-          # - name: mmtk
-          #   mmtk_build: release
+          - name: mmtk
+            mmtk_build: release
         os: [macos-latest, ubuntu-latest]
         include:
           - test_task: check