diff --git a/common.py b/common.py
index 5dda127b..7e50d860 100755
--- a/common.py
+++ b/common.py
@@ -34,7 +34,7 @@
     'main': {
         'llvm-project': 'stable/20211026',
         'swift': 'main',
-        'cmark': 'main',
+        'cmark': 'gfm',
         'ninja': 'release',
         'llbuild': 'main',
         'swiftpm': 'main',