--- a/tests/test-alias.t	Mon Mar 26 22:18:36 2018 -0400
+++ b/tests/test-alias.t	Wed Mar 28 22:04:45 2018 +0900
@@ -616,6 +616,25 @@
   
   (some details hidden, use --verbose to show complete help)
 
+invalid character in user-specified help
+
+  >>> with open('.hg/hgrc', 'ab') as f:
+  ...     f.write(b'[alias]\n'
+  ...             b'invaliddoc = log\n'
+  ...             b'invaliddoc:doc = \xc0\n'
+  ...             b'invalidhelp = log\n'
+  ...             b'invalidhelp:help = \xc0\n') and None
+  $ hg help invaliddoc
+  non-ASCII character in alias definition 'invaliddoc:doc'
+  $ hg help invalidhelp
+  non-ASCII character in alias definition 'invalidhelp:help'
+  $ hg invaliddoc
+  abort: non-ASCII character in alias definition 'invaliddoc:doc'
+  [255]
+  $ hg invalidhelp
+  abort: non-ASCII character in alias definition 'invalidhelp:help'
+  [255]
+
 invalid arguments
 
   $ hg rt foo