diff --git a/Library/Homebrew/brew.h.rb b/Library/Homebrew/brew.h.rb
index ba3c15f05d..8b091995d5 100644
--- a/Library/Homebrew/brew.h.rb
+++ b/Library/Homebrew/brew.h.rb
@@ -619,7 +619,3 @@ def llvm_build
     $1.to_i
   end
 end
-
-def x11_installed?
-  Pathname.new('/usr/X11/lib/libpng.dylib').exist?
-end
diff --git a/Library/Homebrew/brew_doctor.rb b/Library/Homebrew/brew_doctor.rb
index 76177d0683..fddd33a443 100644
--- a/Library/Homebrew/brew_doctor.rb
+++ b/Library/Homebrew/brew_doctor.rb
@@ -54,10 +54,11 @@ def check_for_stray_dylibs
 end
 
 def check_for_x11
-  unless File.exists? '/usr/X11/lib/libpng.dylib'
+  unless x11_installed?
+    opoo "X11 not installed."
     puts <<-EOS.undent
       You don't have X11 installed as part of your Xcode installation.
-      This isn't required for all formula, but is expected by some.
+      This isn't required for all formulae, but is expected by some.
 
     EOS
   end
diff --git a/Library/Homebrew/utils.rb b/Library/Homebrew/utils.rb
index a34e108de2..52b85bd191 100644
--- a/Library/Homebrew/utils.rb
+++ b/Library/Homebrew/utils.rb
@@ -276,4 +276,8 @@ def dump_build_env env
     value = env[k]
     puts "#{k}: #{value}" if value
   end
+end
+
+def x11_installed?
+  Pathname.new('/usr/X11/lib/libpng.dylib').exist?
 end
\ No newline at end of file