diff --git a/mercurial/hook.py b/mercurial/hook.py
--- a/mercurial/hook.py
+++ b/mercurial/hook.py
@@ -91,7 +91,7 @@
     starttime = util.timer()
 
     try:
-        r = obj(ui=ui, repo=repo, hooktype=htype, **args)
+        r = obj(ui=ui, repo=repo, hooktype=htype, **pycompat.strkwargs(args))
     except Exception as exc:
         if isinstance(exc, error.Abort):
             ui.warn(_('error: %s hook failed: %s\n') %