diff --git a/README.rst b/README.rst
index c530422b..d250b6a0 100644
--- a/README.rst
+++ b/README.rst
@@ -649,6 +649,20 @@ override parameters described on resource level.
      #...
    end
 
+NestedValidator
+-------------
+
+You can describe nested parameters in depth if you provide a block with
+description of nested values.
+
+.. code:: ruby
+
+   param :comments, Array, :desc => "User comments" do
+     param :name, String, :desc => "Name of the comment", :required => true
+     param :comment, String, :desc => "Full comment", :required => true
+   end
+
+
 
 Adding custom validator
 -----------------------
diff --git a/lib/apipie/validator.rb b/lib/apipie/validator.rb
index f36b3776..3cc3ecc3 100644
--- a/lib/apipie/validator.rb
+++ b/lib/apipie/validator.rb
@@ -161,8 +161,8 @@ def validate(value)
         @array.include?(value.class)
       end
 
-      def self.build(param_description, argument, options, proc)
-        if argument.is_a?(Array) && argument.first.class == Class
+      def self.build(param_description, argument, options, block)
+        if argument.is_a?(Array) && argument.first.class == Class && !block.is_a?(Proc)
           self.new(param_description, argument)
         end
       end
@@ -273,7 +273,7 @@ def prepare_hash_params
 
 
     # special type of validator: we say that it's not specified
-    class UndefValidator < Apipie::Validator::BaseValidator
+    class UndefValidator < BaseValidator
 
       def validate(value)
         true
@@ -290,7 +290,7 @@ def description
       end
     end
 
-    class NumberValidator < Apipie::Validator::BaseValidator
+    class NumberValidator < BaseValidator
 
       def validate(value)
         self.class.validate(value)
@@ -311,7 +311,7 @@ def self.validate(value)
       end
     end
 
-    class BooleanValidator < Apipie::Validator::BaseValidator
+    class BooleanValidator < BaseValidator
 
       def validate(value)
         %w[true false].include?(value.to_s)
@@ -328,6 +328,41 @@ def description
       end
     end
 
+    class NestedValidator < BaseValidator
+
+      def initialize(param_description, argument, param_group)
+        super(param_description)
+        @validator = Apipie::Validator:: HashValidator.new(param_description, argument, param_group)
+        @type = argument
+      end
+
+      def validate(value)
+        value ||= [] # Rails convert empty array to nil
+        return false if value.class != Array
+        value.each do |child|
+          return false unless @validator.validate(child)
+        end
+        true
+      end
+
+      def process_value(value)
+        value ||= [] # Rails convert empty array to nil
+        @values = []
+        value.each do |child|
+          @values << @validator.process_value(child)
+        end
+        @values
+      end
+
+      def self.build(param_description, argument, options, block)
+        self.new(param_description, block, options[:param_group]) if block.is_a?(Proc) && block.arity == 0 && argument == Array
+      end
+
+      def description
+        "Must be an Array of nested elements"
+      end
+    end
+
   end
 end
 
diff --git a/spec/controllers/users_controller_spec.rb b/spec/controllers/users_controller_spec.rb
index a2043e0b..7b6e80fe 100644
--- a/spec/controllers/users_controller_spec.rb
+++ b/spec/controllers/users_controller_spec.rb
@@ -237,6 +237,67 @@ def compare_hashes(h1, h2)
         assert_response :success
       end
 
+      describe "nested elements"  do
+
+        context "with valid input" do
+          it "should succeed" do
+            put :update,
+                {
+                  :id => 5,
+                  :user => {
+                    :name => "root",
+                    :pass => "12345"
+                  },
+                  :comments => [
+                    {
+                      :comment => 'comment1'
+                    },
+                    {
+                      :comment => 'comment2'
+                    }
+                  ]
+                }
+
+            assert_response :success
+          end
+        end
+        context "with bad input" do
+          it "should raise an error" do
+            expect{ put :update,
+                {
+                  :id => 5,
+                  :user => {
+                    :name => "root",
+                    :pass => "12345"
+                  },
+                  :comments => [
+                    {
+                      :comment => 'comment1'
+                    },
+                    {
+                      :comment => {bad_input: 5}
+                    }
+                  ]
+                }
+            }.to raise_error(Apipie::ParamInvalid)
+          end
+        end
+        it "should work with empty array" do
+          put :update,
+              {
+                :id => 5,
+                :user => {
+                  :name => "root",
+                  :pass => "12345"
+                },
+                :comments => [
+                ]
+              }
+
+          assert_response :success
+        end
+      end
+
     end
   end
 
diff --git a/spec/dummy/app/controllers/users_controller.rb b/spec/dummy/app/controllers/users_controller.rb
index 79615616..be1e41d4 100644
--- a/spec/dummy/app/controllers/users_controller.rb
+++ b/spec/dummy/app/controllers/users_controller.rb
@@ -220,8 +220,11 @@ def create
     render :text => "OK #{params.inspect}"
   end
 
-  api :PUT, "/users/:id", "Create user"
+  api :PUT, "/users/:id", "Update an user"
   param_group :user
+  param :comments, Array do
+    param :comment, String
+  end
   def update
     render :text => "OK #{params.inspect}"
   end