diff --git a/lib/fluent/plugin_helper/storage.rb b/lib/fluent/plugin_helper/storage.rb
index 32b8a1f5c7..f3f6d92920 100644
--- a/lib/fluent/plugin_helper/storage.rb
+++ b/lib/fluent/plugin_helper/storage.rb
@@ -30,6 +30,10 @@ module Storage
       StorageState = Struct.new(:storage, :running)
 
       def storage_create(usage: '', type: nil, conf: nil, default_type: nil)
+        if conf && !conf.arg.empty?
+          usage = conf.arg
+        end
+
         s = @_storages[usage]
         if s && s.running
           return s.storage
@@ -72,7 +76,7 @@ def storage_create(usage: '', type: nil, conf: nil, default_type: nil)
       module StorageParams
         include Fluent::Configurable
         # minimum section definition to instantiate storage plugin instances
-        config_section :storage, required: false, multi: true, param_name: :storage_configs do
+        config_section :storage, required: false, multi: true, param_name: :storage_configs, init: true do
           config_argument :usage, :string, default: ''
           config_param    :@type, :string, default: Fluent::Plugin::Storage::DEFAULT_TYPE
         end
@@ -194,6 +198,10 @@ def initialize(storage)
         def_delegators :@storage, :start, :stop, :before_shutdown, :shutdown, :after_shutdown, :close, :terminate
         def_delegators :@storage, :started?, :stopped?, :before_shutdown?, :shutdown?, :after_shutdown?, :closed?, :terminated?
 
+        def method_missing(name, *args)
+          @monitor.synchronize{ @storage.__send__(name, *args) }
+        end
+
         def persistent_always?
           true
         end
@@ -274,7 +282,7 @@ class SynchronizeWrapper
 
         def initialize(storage)
           @storage = storage
-          @mutex = Mutex.new
+          @monitor = Monitor.new
         end
 
         def_delegators :@storage, :persistent, :autosave, :autosave_interval, :save_at_shutdown
@@ -282,6 +290,10 @@ def initialize(storage)
         def_delegators :@storage, :start, :stop, :before_shutdown, :shutdown, :after_shutdown, :close, :terminate
         def_delegators :@storage, :started?, :stopped?, :before_shutdown?, :shutdown?, :after_shutdown?, :closed?, :terminated?
 
+        def method_missing(name, *args)
+          @monitor.synchronize{ @storage.__send__(name, *args) }
+        end
+
         def synchronized?
           true
         end
@@ -291,35 +303,35 @@ def implementation
         end
 
         def load
-          @mutex.synchronize do
+          @monitor.synchronize do
             @storage.load
           end
         end
 
         def save
-          @mutex.synchronize do
+          @monitor.synchronize do
             @storage.save
           end
         end
 
         def get(key)
-          @mutex.synchronize{ @storage.get(key) }
+          @monitor.synchronize{ @storage.get(key) }
         end
 
         def fetch(key, defval)
-          @mutex.synchronize{ @storage.fetch(key, defval) }
+          @monitor.synchronize{ @storage.fetch(key, defval) }
         end
 
         def put(key, value)
-          @mutex.synchronize{ @storage.put(key, value) }
+          @monitor.synchronize{ @storage.put(key, value) }
         end
 
         def delete(key)
-          @mutex.synchronize{ @storage.delete(key) }
+          @monitor.synchronize{ @storage.delete(key) }
         end
 
         def update(key, &block)
-          @mutex.synchronize do
+          @monitor.synchronize do
             v = block.call(@storage.get(key))
             @storage.put(key, v)
             v
diff --git a/test/plugin_helper/test_storage.rb b/test/plugin_helper/test_storage.rb
index ead7fa21ba..7f36329acc 100644
--- a/test/plugin_helper/test_storage.rb
+++ b/test/plugin_helper/test_storage.rb
@@ -102,7 +102,8 @@ class Dummy2 < Fluent::Plugin::TestBase
   test 'can override default configuration parameters, but not overwrite whole definition' do
     d = Dummy.new
     d.configure(config_element())
-    assert_equal [], d.storage_configs
+    assert_equal 1, d.storage_configs.size
+    assert_equal 'local', d.storage_configs.first[:@type]
 
     d = Dummy2.new
     d.configure(config_element('ROOT', '', {}, [config_element('storage', '', {}, [])]))
@@ -130,7 +131,7 @@ class Dummy2 < Fluent::Plugin::TestBase
     d = Dummy2.new
     d.configure(config_element())
     assert_raise Fluent::ConfigError.new("@type is required in <storage>") do
-      d.storage_create(conf: config_element('storage', '', {}), default_type: 'ex2')
+      d.storage_create(conf: config_element('storage', 'foo', {}), default_type: 'ex2')
     end
   end
 
@@ -139,7 +140,7 @@ class Dummy2 < Fluent::Plugin::TestBase
     assert_nothing_raised do
       d.configure(config_element())
     end
-    assert_equal 0, d._storages.size
+    assert_equal 1, d._storages.size
   end
 
   test 'can be configured with a storage section' do