diff --git a/gclient.py b/gclient.py
index 4f3ee24f5..119527a7f 100755
--- a/gclient.py
+++ b/gclient.py
@@ -3491,6 +3491,9 @@ def CMDgrep(parser, args):
             file=sys.stderr)
         return 1
 
+    if gclient_utils.IsEnvCog():
+        raise gclient_utils.Error('gclient grep command is not supported.')
+
     jobs_arg = ['--jobs=1']
     if re.match(r'(-j|--jobs=)\d+$', args[0]):
         jobs_arg, args = args[:1], args[1:]