diff --git a/subcmds/sync.py b/subcmds/sync.py
index afd44da..1537c9a 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -118,6 +118,8 @@
         print >>sys.stderr, 'error: Cannot fetch %s' % project.name
         sys.exit(1)
     pm.end()
+    for project in projects:
+      project.bare_git.gc('--auto')
     return fetched
 
   def UpdateProjectList(self):