diff --git a/contrib/check-code.py b/contrib/check-code.py
--- a/contrib/check-code.py
+++ b/contrib/check-code.py
@@ -119,6 +119,7 @@
     (r'\[[^\]]+==', '[ foo == bar ] is a bashism, use [ foo = bar ] instead'),
     (r'(^|\|\s*)grep (-\w\s+)*[^|]*[(|]\w',
      "use egrep for extended grep syntax"),
+    (r'(^|\|\s*)e?grep .*\\S', "don't use \\S in regular expression"),
     (r'(?<!!)/bin/', "don't use explicit paths for tools"),
     (r'#!.*/bash', "don't use bash in shebang, use sh"),
     (r'[^\n]\Z', "no trailing newline"),
diff --git a/tests/test-context-metadata.t b/tests/test-context-metadata.t
--- a/tests/test-context-metadata.t
+++ b/tests/test-context-metadata.t
@@ -36,7 +36,7 @@
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     Changed
   
-  $ hg --config extensions.metaedit=$TESTTMP/metaedit.py metaedit 'parents=0' 2>&1 | egrep '^\S*Error'
+  $ hg --config extensions.metaedit=$TESTTMP/metaedit.py metaedit 'parents=0' 2>&1 | egrep '^RuntimeError'
   RuntimeError: can't reuse the manifest: its p1 doesn't match the new ctx p1
 
   $ hg --config extensions.metaedit=$TESTTMP/metaedit.py metaedit 'user=foo <foo@example.com>'