diff --git a/lib/redmine/plugin.rb b/lib/redmine/plugin.rb
index 7f058a31d..3f2d0e8f9 100644
--- a/lib/redmine/plugin.rb
+++ b/lib/redmine/plugin.rb
@@ -19,6 +19,7 @@ module Redmine #:nodoc:
 
   class PluginNotFound < StandardError; end
   class PluginRequirementError < StandardError; end
+  class PluginIdDuplicated < StandardError; end
 
   # Base class for Redmine plugins.
   # Plugins are registered using the <tt>register</tt> class method that acts as the public constructor.
@@ -72,6 +73,9 @@ module Redmine #:nodoc:
     # Plugin constructor
     def self.register(id, &block)
       p = new(id)
+      if installed?(p.id)
+        raise PluginIdDuplicated.new("#{p.id} plugin was already registered.")
+      end
       p.instance_eval(&block)
 
       # Set a default name if it was not provided during registration
@@ -152,7 +156,11 @@ module Redmine #:nodoc:
           end
           initializer = File.join(directory, "init.rb")
           if File.file?(initializer)
-            require initializer
+            begin
+              require initializer
+            rescue => e
+              Rails.logger.warn("plugin loading failed. skip loading. message: #{e.message}")
+            end
           end
         end
       end
diff --git a/test/functional/settings_controller_test.rb b/test/functional/settings_controller_test.rb
index 4c1019191..6331622bc 100644
--- a/test/functional/settings_controller_test.rb
+++ b/test/functional/settings_controller_test.rb
@@ -29,6 +29,7 @@ class SettingsControllerTest < Redmine::ControllerTest
   def teardown
     Setting.delete_all
     Setting.clear_cache
+    Redmine::Plugin.clear
   end
 
   def test_index
diff --git a/test/unit/lib/redmine/plugin_test.rb b/test/unit/lib/redmine/plugin_test.rb
index 51ae269be..3ccccf2de 100644
--- a/test/unit/lib/redmine/plugin_test.rb
+++ b/test/unit/lib/redmine/plugin_test.rb
@@ -52,6 +52,40 @@ class Redmine::PluginTest < ActiveSupport::TestCase
     assert_equal '0.0.1', plugin.version
   end
 
+  def test_register_fail
+    @klass.register :foo do
+      name 'Foo plugin'
+      url 'http://example.net/plugins/foo'
+      author 'John Smith'
+      author_url 'http://example.net/jsmith'
+      version '0.0.1'
+    end
+
+    assert_equal 1, @klass.all.size
+
+    assert_raise Redmine::PluginIdDuplicated do
+      @klass.register :foo do
+        name 'Yet Another Foo plugin'
+        url 'http://example.net/plugins/ya_foo'
+        author 'Joe Bloggs'
+        author_url 'http://example.net/jbloggs'
+        version '1.0.0'
+      end
+    end
+    assert_equal 1, @klass.all.size
+
+    assert_nothing_raised do
+      @klass.register :ya_foo do
+        name 'Yet Another Foo plugin'
+        url 'http://example.net/plugins/ya_foo'
+        author 'Joe Bloggs'
+        author_url 'http://example.net/jbloggs'
+        version '1.0.0'
+      end
+    end
+    assert_equal 2, @klass.all.size
+  end
+
   def test_installed
     @klass.register(:foo) {}
     assert_equal true, @klass.installed?(:foo)