diff --git a/lib/dry/container/item.rb b/lib/dry/container/item.rb
index dc01875..e215405 100644
--- a/lib/dry/container/item.rb
+++ b/lib/dry/container/item.rb
@@ -23,6 +23,27 @@ def initialize(item, options = {})
       def call
         raise NotImplementedError
       end
+
+      # @private
+      def value?
+        !callable?
+      end
+
+      # @private
+      def callable?
+        options[:call]
+      end
+
+      # Build a new item with transformation applied
+      #
+      # @private
+      def map(func)
+        if callable?
+          self.class.new(-> { func.(item.call) }, options)
+        else
+          self.class.new(func.(item), options)
+        end
+      end
     end
   end
 end
diff --git a/lib/dry/container/item/callable.rb b/lib/dry/container/item/callable.rb
index c0d5e1c..eafdaa5 100644
--- a/lib/dry/container/item/callable.rb
+++ b/lib/dry/container/item/callable.rb
@@ -14,13 +14,6 @@ class Callable < Item
         def call
           callable? ? item.call : item
         end
-
-        private
-
-        # @private
-        def callable?
-          options[:call]
-        end
       end
     end
   end
diff --git a/lib/dry/container/item/memoizable.rb b/lib/dry/container/item/memoizable.rb
index ce1f752..d8ebb3a 100644
--- a/lib/dry/container/item/memoizable.rb
+++ b/lib/dry/container/item/memoizable.rb
@@ -21,7 +21,7 @@ class Memoizable < Item
         # @return [Dry::Container::Item::Base]
         def initialize(item, options = {})
           super
-          raise_not_supported_error unless item.is_a?(::Proc)
+          raise_not_supported_error unless callable?
 
           @memoize_mutex = ::Mutex.new
         end
diff --git a/lib/dry/container/mixin.rb b/lib/dry/container/mixin.rb
index 3efc9aa..a170aa1 100644
--- a/lib/dry/container/mixin.rb
+++ b/lib/dry/container/mixin.rb
@@ -6,6 +6,9 @@ class Container
     PREFIX_NAMESPACE = lambda do |namespace, key, config|
       [namespace, key].join(config.namespace_separator)
     end
+
+    EMPTY_HASH = {}.freeze
+
     # Mixin to expose Inversion of Control (IoC) container behaviour
     #
     # @example
@@ -90,7 +93,7 @@ def config
       # @return [Dry::Container::Mixin] self
       #
       # @api public
-      def register(key, contents = nil, options = {}, &block)
+      def register(key, contents = nil, options = EMPTY_HASH, &block)
         if block_given?
           item = block
           options = contents if contents.is_a?(::Hash)
@@ -208,23 +211,22 @@ def each(&block)
       # @return [Dry::Container::Mixin] self
       #
       # @api public
-      def decorate(key, with:)
-        original = _container.delete(key.to_s) do
+      def decorate(key, with: nil, &block)
+        key = key.to_s
+        original = _container.delete(key) do
           raise Error, "Nothing registered with the key #{key.inspect}"
         end
 
-        decorator = with
-        memoize = original.is_a?(Item::Memoizable)
-
-        if decorator.is_a?(Class)
-          decorated = -> { decorator.new(original.call) }
-        elsif decorator.respond_to?(:call)
-          decorated = -> { decorator.call(original.call) }
+        if with.is_a?(Class)
+          decorator = with.method(:new)
+        elsif block.nil? && !with.respond_to?(:call)
+          raise Error, "Decorator needs to be a Class, block, or respond to the `call` method"
         else
-          raise Error, "Decorator needs to be a Class or responds to the `call` method"
+          decorator = with || block
         end
 
-        register(key, memoize: memoize, &decorated)
+        _container[key] = original.map(decorator)
+        self
       end
 
       # Evaluate block and register items in namespace
diff --git a/spec/support/shared_examples/container.rb b/spec/support/shared_examples/container.rb
index cbde23a..8e7b0ee 100644
--- a/spec/support/shared_examples/container.rb
+++ b/spec/support/shared_examples/container.rb
@@ -426,14 +426,34 @@
       end
 
       context 'for not callable item' do
-        before do
-          container.register(key, call: false) { "value" }
-          container.decorate(key, with: SimpleDelegator)
+        describe 'wrapping' do
+          before do
+            container.register(key, call: false) { "value" }
+            container.decorate(key, with: SimpleDelegator)
+          end
+
+          it 'expected to be an instance of SimpleDelegator' do
+            expect(container.resolve(key)).to be_instance_of(SimpleDelegator)
+            expect(container.resolve(key).__getobj__.call).to eql("value")
+          end
         end
 
-        it 'expected to be an instance of SimpleDelegator' do
-          expect(container.resolve(key)).to be_instance_of(SimpleDelegator)
-          expect(container.resolve(key).__getobj__.call).to eql("value")
+        describe 'memoization' do
+          before do
+            @called = 0
+            container.register(key, 'value')
+
+            container.decorate(key) do |value|
+              @called += 1
+              "<#{value}>"
+            end
+          end
+
+          it 'decorates static value only once' do
+            expect(container.resolve(key)).to eql('<value>')
+            expect(container.resolve(key)).to eql('<value>')
+            expect(@called).to be(1)
+          end
         end
       end