diff --git a/Library/Homebrew/os/mac/xquartz.rb b/Library/Homebrew/os/mac/xquartz.rb
index 6ac970b188cb03c705a96df5bfa64d0cbc978ffb..3147dc1dfc070d23766b1ced649f4010888cc143 100644
--- a/Library/Homebrew/os/mac/xquartz.rb
+++ b/Library/Homebrew/os/mac/xquartz.rb
@@ -99,6 +99,9 @@ module OS
           Pathname.new("/opt/X11")
         elsif Pathname.new("/usr/X11/lib/libpng.dylib").exist?
           Pathname.new("/usr/X11")
+        # X11 doesn't include libpng on Tiger
+        elsif Pathname.new("/usr/X11R6/lib/libX11.dylib").exist?
+          Pathname.new("/usr/X11R6")
         end
       end