--- a/tests/test-fileset.t	Sat Jan 13 15:07:37 2018 +0900
+++ b/tests/test-fileset.t	Sat Jan 13 15:13:29 2018 +0900
@@ -68,6 +68,17 @@
     None)
   hg: parse error: not a symbol
   [255]
+  $ fileset -v -- '-x'
+  (negate
+    (symbol 'x'))
+  hg: parse error: can't use negate operator in this context
+  [255]
+  $ fileset -v -- '-()'
+  (negate
+    (group
+      None))
+  hg: parse error: can't use negate operator in this context
+  [255]
 
 Test files status