diff --git a/logstash-core/lib/logstash/plugin.rb b/logstash-core/lib/logstash/plugin.rb
index a1856eef5..715b28587 100644
--- a/logstash-core/lib/logstash/plugin.rb
+++ b/logstash-core/lib/logstash/plugin.rb
@@ -121,10 +121,8 @@ class LogStash::Plugin
   # This is keep for backward compatibility, the logic was moved into the registry class
   # but some plugins use this method to return a specific instance on lookup
   #
-  #
-  #
   # Should I remove this now and make sure the pipeline invoke the Registry or I should wait for 6.0
-  # Its not really part of the public api but its used by the tests.
+  # Its not really part of the public api but its used by the tests a lot to mock the plugins.
   def self.lookup(type, name)
     LogStash::PluginRegistry.lookup_pipeline_plugin(type, name)
   end
diff --git a/logstash-core/lib/logstash/plugins/registry.rb b/logstash-core/lib/logstash/plugins/registry.rb
index 422c494e9..a8ec46a5e 100644
--- a/logstash-core/lib/logstash/plugins/registry.rb
+++ b/logstash-core/lib/logstash/plugins/registry.rb
@@ -137,7 +137,7 @@ module LogStash module Plugins
       if plugin.nil?
         begin
           path = "logstash/#{type}s/#{plugin_name}"
-          require path
+          require path rescue LoadError # Plugin might be already defined in the current scope
           klass = namespace_lookup(type, plugin_name)
           plugin = lazy_add(type, plugin_name, klass)
         rescue => e
@@ -170,7 +170,7 @@ module LogStash module Plugins
     end
 
     def lazy_add(type, name, klass)
-      logger.error("Lazy Adding plugin to the registry", :name => name, :type => type, :class => klass)
+      logger.error("On demand adding plugin to the registry", :name => name, :type => type, :class => klass)
       add_plugin(type, name, klass)
     end
 
diff --git a/logstash-core/spec/api/spec_helper.rb b/logstash-core/spec/api/spec_helper.rb
index 8e4912ddf..31ec6f271 100644
--- a/logstash-core/spec/api/spec_helper.rb
+++ b/logstash-core/spec/api/spec_helper.rb
@@ -5,6 +5,7 @@ require "stud/task"
 require "logstash/devutils/rspec/spec_helper"
 $LOAD_PATH.unshift(File.expand_path(File.dirname(__FILE__)))
 require "lib/api/support/resource_dsl_methods"
+require_relative "../support/mocks_classes"
 require 'rspec/expectations'
 require "logstash/settings"
 require 'rack/test'
diff --git a/logstash-core/spec/support/mocks_classes.rb b/logstash-core/spec/support/mocks_classes.rb
index d90318d53..f16d74737 100644
--- a/logstash-core/spec/support/mocks_classes.rb
+++ b/logstash-core/spec/support/mocks_classes.rb
@@ -2,6 +2,7 @@
 require "logstash/outputs/base"
 require "thread"
 
+module LogStash module Outputs
 class DummyOutput < LogStash::Outputs::Base
   config_name "dummyoutput"
   milestone 2
@@ -47,3 +48,4 @@ class DummyOutputWithEventsArray < LogStash::Outputs::Base
   def close
   end
 end
+end end