diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index c4437f0fd54e269d10f1f8d0a4755e3b9eac2635..fe5bb84cf688270be1fa95a862b001a0cf1d580d 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -250,6 +250,7 @@ module OS
       "5.0.1" => { :clang => "5.0", :clang_build => 500 },
       "5.0.2" => { :clang => "5.0", :clang_build => 500 },
       "5.1"   => { :clang => "5.1", :clang_build => 503 },
+      "5.1.1" => { :clang => "5.1", :clang_build => 503 },
     }
 
     def compilers_standard?