diff --git a/subcmds/selfupdate.py b/subcmds/selfupdate.py
index 4f46a12..46aa3a1 100644
--- a/subcmds/selfupdate.py
+++ b/subcmds/selfupdate.py
@@ -55,6 +55,7 @@
         print >>sys.stderr, "error: can't update repo"
         sys.exit(1)
 
+      rp.bare_git.gc('--auto')
       _PostRepoFetch(rp,
                      no_repo_verify = opt.no_repo_verify,
                      verbose = True)
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 80bba1a..36ef16d 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -185,6 +185,8 @@
         t.join()
 
     pm.end()
+    for project in projects:
+      project.bare_git.gc('--auto')
     return fetched
 
   def UpdateProjectList(self):