diff --git a/Library/Homebrew/extend/os/mac/diagnostic.rb b/Library/Homebrew/extend/os/mac/diagnostic.rb
index 5d5e2eec9b..3116255fa2 100644
--- a/Library/Homebrew/extend/os/mac/diagnostic.rb
+++ b/Library/Homebrew/extend/os/mac/diagnostic.rb
@@ -139,7 +139,11 @@ module Homebrew
       end
 
       def check_ruby_version
-        ruby_version = "2.3.7"
+        ruby_version = if MacOS.version >= :catalina
+          "2.6.3"
+        else
+          "2.3.7"
+        end
         return if RUBY_VERSION == ruby_version
         return if ARGV.homebrew_developer? && OS::Mac.prerelease?