diff --git a/pre-upload.py b/pre-upload.py
index 5752d16..b4f00f7 100755
--- a/pre-upload.py
+++ b/pre-upload.py
@@ -326,13 +326,17 @@
 
 def _check_change_has_bug_field(project, commit):
   """Check for a correctly formatted 'BUG=' field in the commit message."""
-  BUG_RE = r'\nBUG=([Nn]one|(chrome-os-partner|chromium|chromium-os):\d+)'
+  OLD_BUG_RE = r'\nBUG=.*chromium-os'
+  if re.search(OLD_BUG_RE, _get_commit_desc(commit)):
+    msg = ('The chromium-os bug tracker is now deprecated. Please use\n'
+           'the chromium tracker in your BUG= line now.')
+    return HookFailure(msg)
 
+  BUG_RE = r'\nBUG=([Nn]one|(chrome-os-partner|chromium):\d+)'
   if not re.search(BUG_RE, _get_commit_desc(commit)):
     msg = ('Changelist description needs BUG field (after first line):\n'
-           'BUG=chromium-os:9999 (for public tracker)\n'
+           'BUG=chromium:9999 (for public tracker)\n'
            'BUG=chrome-os-partner:9999 (for partner tracker)\n'
-           'BUG=chromium:9999 (for browser tracker)\n'
            'BUG=None')
     return HookFailure(msg)