diff --git a/Library/Homebrew/cmd/doctor.rb b/Library/Homebrew/cmd/doctor.rb
index 9f47dd92a0..af364f0c8f 100644
--- a/Library/Homebrew/cmd/doctor.rb
+++ b/Library/Homebrew/cmd/doctor.rb
@@ -199,6 +199,9 @@ def check_xcode_exists
 end
 
 def check_for_latest_xcode
+  # the check_xcode_exists check is enough
+  return if MacOS.xcode_version.nil?
+
   latest_xcode = case MacOS.version
     when 10.5 then "3.1.4"
     when 10.6 then "3.2.6"