Check Puma.respond_to?(:cli_config) first

config/initializers/validate_puma.rb

 # frozen_string_literal: true
 
-def max_puma_workers
-  Puma.cli_config.options[:workers].to_i
-end
-
 if Gitlab::Runtime.puma? && !Gitlab::Runtime.puma_in_clustered_mode?
   raise 'Puma is only supported in Clustered mode (workers > 0)' if Gitlab.com?
 

lib/gitlab/runtime.rb

@@ -82,7 +82,10 @@ module Gitlab
       end
 
       def puma_in_clustered_mode?
-        puma? && Puma.cli_config.options[:workers].to_i > 0
+        return unless puma?
+        return unless Puma.respond_to?(:cli_config)
+
+        Puma.cli_config.options[:workers].to_i > 0
       end
 
       def max_threads