diff --git a/git_cache.py b/git_cache.py
index ab3d08926..f1cecf766 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -592,6 +592,13 @@ class Mirror(object):
       return
 
     # Run Garbage Collect to compress packfile.
+    # It appears core.deltaBaseCacheLimit restricts the file size of the pack
+    # files produced, while we want 1 big pack file for efficiency.
+    try:
+      self.RunGit(['config', '--unset-all', 'core.deltaBaseCacheLimit'],
+                  cwd=cwd)
+    except subprocess.CalledProcessError:
+      pass  # Nothing to unset is fine.
     gc_args = ['gc', '--prune=all']
     if gc_aggressive:
       gc_args.append('--aggressive')