diff --git a/Library/Homebrew/caveats.rb b/Library/Homebrew/caveats.rb
index 926614d0a0..526cb8a1ca 100644
--- a/Library/Homebrew/caveats.rb
+++ b/Library/Homebrew/caveats.rb
@@ -95,7 +95,7 @@ class Caveats
           s << "    launchctl load #{plist_link}"
         end
       end
-      s << '' << "WARNING: launchctl will fail when run under tmux."
+      s << '' << "WARNING: launchctl will fail when run under tmux." if ENV['TMUX']
     end
     s.join("\n") unless s.empty?
   end