diff --git a/mercurial/parser.py b/mercurial/parser.py
--- a/mercurial/parser.py
+++ b/mercurial/parser.py
@@ -135,8 +135,9 @@ def buildargsdict(trees, funcname, argsp
         raise error.ParseError(_("%(func)s takes at least %(nargs)d positional "
                                  "arguments")
                                % {'func': funcname, 'nargs': len(poskeys)})
-    if not varkey and len(trees) > len(poskeys) + len(keys):
-        raise error.ParseError(_("%(func)s takes at most %(nargs)d arguments")
+    if not varkey and kwstart > len(poskeys) + len(keys):
+        raise error.ParseError(_("%(func)s takes at most %(nargs)d positional "
+                                 "arguments")
                                % {'func': funcname,
                                   'nargs': len(poskeys) + len(keys)})
     args = {}
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -454,7 +454,7 @@ keyword arguments
   0
 
   $ log 'extra(branch, a, b)'
-  hg: parse error: extra takes at most 2 arguments
+  hg: parse error: extra takes at most 2 positional arguments
   [255]
   $ log 'extra(a, label=b)'
   hg: parse error: extra got multiple values for keyword argument 'label'