1 files changed, 3 insertions, 0 deletions

diff --git a/subcmds/diffmanifests.py b/subcmds/diffmanifests.py
index f6cc30a2..0e5f4108 100644
--- a/subcmds/diffmanifests.py
+++ b/subcmds/diffmanifests.py
@@ -179,6 +179,9 @@ synced and their revisions won't be found.
   def ValidateOptions(self, opt, args):
     if not args or len(args) > 2:
       self.OptionParser.error('missing manifests to diff')
+    if opt.this_manifest_only is False:
+      raise self.OptionParser.error(
+          '`diffmanifest` only supports the current tree')
 
   def Execute(self, opt, args):
     self.out = _Coloring(self.client.globalConfig)