diff --git a/hgext/largefiles/overrides.py b/hgext/largefiles/overrides.py
--- a/hgext/largefiles/overrides.py
+++ b/hgext/largefiles/overrides.py
@@ -50,8 +50,10 @@ def composenormalfilematcher(match, mani
 
 def installnormalfilesmatchfn(manifest):
     '''installmatchfn with a matchfn that ignores all largefiles'''
-    def overridematch(ctx, pats=(), opts={}, globbed=False,
+    def overridematch(ctx, pats=(), opts=None, globbed=False,
             default='relpath', badfn=None):
+        if opts is None:
+            opts = {}
         match = oldmatch(ctx, pats, opts, globbed, default, badfn=badfn)
         return composenormalfilematcher(match, manifest)
     oldmatch = installmatchfn(overridematch)