diff --git a/mercurial/minifileset.py b/mercurial/minifileset.py
--- a/mercurial/minifileset.py
+++ b/mercurial/minifileset.py
@@ -30,7 +30,7 @@ def _compile(tree):
             pl = len(p)
             f = lambda n, s: n.startswith(p) and (len(n) == pl or n[pl] == '/')
             return f
-        raise error.ParseError(_("unsupported file pattern"),
+        raise error.ParseError(_("unsupported file pattern: %s") % name,
                                hint=_('paths must be prefixed with "path:"'))
     elif op == 'or':
         func1 = _compile(tree[1])
diff --git a/tests/test-lfs.t b/tests/test-lfs.t
--- a/tests/test-lfs.t
+++ b/tests/test-lfs.t
@@ -18,6 +18,10 @@
 # Commit small file
   $ echo s > smallfile
   $ echo '**.py = LF' > .hgeol
+  $ hg --config lfs.track='"size(\">1000B\")"' commit -Aqm "add small file"
+  hg: parse error: unsupported file pattern: size(">1000B")
+  (paths must be prefixed with "path:")
+  [255]
   $ hg --config lfs.track='size(">1000B")' commit -Aqm "add small file"
 
 # Commit large file