diff --git a/CHANGELOG.md b/CHANGELOG.md
index 31b6c971..17824f9f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,8 +1,9 @@
 # Changelog
 
 ## Unreleased
-- No longer merge parameter schemas per of the same location (for example "query") in order to fix https://github.com/ahx/openapi_first/issues/320
 
+- Middlewares now accept the OAD as a first positional argument instead of `:spec` inside the options hash.
+- No longer merge parameter schemas per of the same location (for example "query") in order to fix https://github.com/ahx/openapi_first/issues/320
 - `OpenapiFirst::Test::Methods[MyApplication]` returns a Module which adds an `app` method to be used by rack-test alonside the `assert_api_conform` method.
 - Make default coverage report less verbose
   The default formatter (TerminalFormatter) no longer prints all un-requested requests by default. You can set `test.coverage_formatter_options = { focused: false }` to get back the old behavior
diff --git a/lib/openapi_first/middlewares/request_validation.rb b/lib/openapi_first/middlewares/request_validation.rb
index eddf44f2..bfca5ebe 100644
--- a/lib/openapi_first/middlewares/request_validation.rb
+++ b/lib/openapi_first/middlewares/request_validation.rb
@@ -6,19 +6,26 @@ module Middlewares
     # A Rack middleware to validate requests against an OpenAPI API description
     class RequestValidation
       # @param app The parent Rack application
-      # @param options An optional Hash of configuration options to override defaults
+      # @param spec [String, OpenapiFirst::Definition] Path to the OpenAPI file or an instance of Definition.
+      # @param options Hash
+      #   :spec [String, OpenapiFirst::Definition] Path to the OpenAPI file or an instance of Definition.
+      #         This will be deprecated. Please use spec argument instead.
       #   :raise_error    A Boolean indicating whether to raise an error if validation fails.
       #                   default: false
       #   :error_response The Class to use for error responses.
       #                   This can be a Symbol-name of an registered error response (:default, :jsonapi)
       #                   or it can be set to false to disable returning a response.
       #                   default: OpenapiFirst::Plugins::Default::ErrorResponse (Config.default_options.error_response)
-      def initialize(app, options = {})
+      def initialize(app, spec = nil, options = {})
         @app = app
+        if spec.is_a?(Hash)
+          options = spec
+          spec = options.fetch(:spec)
+        end
         @raise = options.fetch(:raise_error, OpenapiFirst.configuration.request_validation_raise_error)
         @error_response_class = error_response_option(options[:error_response])
 
-        spec = options.fetch(:spec)
+        spec ||= options.fetch(:spec)
         raise "You have to pass spec: when initializing #{self.class}" unless spec
 
         @definition = spec.is_a?(Definition) ? spec : OpenapiFirst.load(spec)
diff --git a/lib/openapi_first/middlewares/response_validation.rb b/lib/openapi_first/middlewares/response_validation.rb
index 454dda2c..21fe7dcb 100644
--- a/lib/openapi_first/middlewares/response_validation.rb
+++ b/lib/openapi_first/middlewares/response_validation.rb
@@ -6,15 +6,19 @@ module OpenapiFirst
   module Middlewares
     # A Rack middleware to validate requests against an OpenAPI API description
     class ResponseValidation
-      # @param app The parent Rack application
+      # @param spec [String, OpenapiFirst::Definition] Path to the OpenAPI file or an instance of Definition
       # @param options Hash
-      #   :spec [String, OpenapiFirst::Definition] Path to the OpenAPI file or an instance of Definition
+      #   :spec [String, OpenapiFirst::Definition] Path to the OpenAPI file or an instance of Definition.
+      #         This will be deprecated. Please use spec argument instead.
       #   :raise_error [Boolean] Whether to raise an error if validation fails. default: true
-      def initialize(app, options = {})
+      def initialize(app, spec = nil, options = {})
         @app = app
+        if spec.is_a?(Hash)
+          options = spec
+          spec = options.fetch(:spec)
+        end
         @raise = options.fetch(:raise_error, OpenapiFirst.configuration.response_validation_raise_error)
 
-        spec = options.fetch(:spec)
         raise "You have to pass spec: when initializing #{self.class}" unless spec
 
         @definition = spec.is_a?(Definition) ? spec : OpenapiFirst.load(spec)
diff --git a/spec/middlewares/request_validation_spec.rb b/spec/middlewares/request_validation_spec.rb
index 96793de9..258d4057 100644
--- a/spec/middlewares/request_validation_spec.rb
+++ b/spec/middlewares/request_validation_spec.rb
@@ -32,6 +32,22 @@
     end
   end
 
+  context 'when OAD is passed as first argument' do
+    let(:app) do
+      Rack::Builder.app do
+        use(OpenapiFirst::Middlewares::RequestValidation, File.expand_path('../data/petstore-expanded.yaml', __dir__))
+        run ->(_) {}
+      end
+    end
+
+    it 'returns 400 is request is invalid' do
+      header 'Content-Type', 'application/json'
+      post '/pets', 'not json'
+
+      expect(last_response.status).to eq 400
+    end
+  end
+
   context 'when parameter is invalid' do
     it 'returns 400' do
       get '/pets?limit=three'
diff --git a/spec/middlewares/response_validation_spec.rb b/spec/middlewares/response_validation_spec.rb
index a777b2ac..dacb5076 100644
--- a/spec/middlewares/response_validation_spec.rb
+++ b/spec/middlewares/response_validation_spec.rb
@@ -25,6 +25,26 @@
   end
   let(:response) { Rack::Response.new(response_body, status, headers) }
 
+  context 'with path to OAD as first argument' do
+    let(:response_body) { '2' }
+
+    let(:app) do
+      res = response
+      definition = spec
+      Rack::Builder.app do
+        use Rack::Lint
+        use OpenapiFirst::Middlewares::ResponseValidation, definition
+        run ->(_env) { res.finish }
+      end
+    end
+
+    it 'fails if request is inavlid' do
+      expect do
+        get '/pets'
+      end.to raise_error OpenapiFirst::ResponseInvalidError
+    end
+  end
+
   context 'without content-type header' do
     let(:headers) do
       { 'X-HEAD' => '/api/next-page' }