diff --git a/examples/rack_routes.rb b/examples/rack_routes.rb
index 75a9327b..cd6d7465 100755
--- a/examples/rack_routes.rb
+++ b/examples/rack_routes.rb
@@ -33,6 +33,13 @@ def response(env)
   end
 end
 
+class BigNumber < Goliath::API
+  use Goliath::Rack::Params
+  def response(env)
+    [200, {}, "big number #{params[:number]}!"]
+  end
+end
+
 class Bonjour < Goliath::API
   def response(env)
     [200, {}, "bonjour!"]
@@ -81,7 +88,11 @@ class RackRoutes < Goliath::API
   map "/aloha", Aloha
 
   map "/:number", :number => /\d+/ do
-    run HelloNumber.new
+    if params[:number].to_i > 100
+      run BigNumber.new
+    else
+      run HelloNumber.new
+    end
   end
 
   map '/' do
diff --git a/lib/goliath/rack/builder.rb b/lib/goliath/rack/builder.rb
index fcaf556d..5fcf1057 100644
--- a/lib/goliath/rack/builder.rb
+++ b/lib/goliath/rack/builder.rb
@@ -2,14 +2,17 @@
 
 module Goliath
   module Rack
-    class Builder
+    class Builder < ::Rack::Builder
+      attr_accessor :params
+      include Params::Parser
+
       # Builds the rack middleware chain for the given API
       #
       # @param klass [Class] The API class to build the middlewares for
       # @param api [Object] The instantiated API
       # @return [Object] The Rack middleware chain
       def self.build(klass, api)
-        ::Rack::Builder.app do
+        Builder.app do
           klass.middlewares.each do |mw_klass, args, blk|
             use(mw_klass, *args, &blk)
           end
@@ -19,9 +22,12 @@ def self.build(klass, api)
                 run Builder.build(route_klass, route_klass.new)
               }
               klass.router.add(path, opts.dup).to {|env|
+                builder = Builder.new
                 env['params'] ||= {}
                 env['params'].merge!(env['router.params'])
-                ::Rack::Builder.new(&blk).to_app.call(env)
+                builder.params = builder.retrieve_params(env)
+                builder.instance_eval(&blk)
+                builder.to_app.call(env)
               }
             end
             run klass.router
diff --git a/lib/goliath/rack/params.rb b/lib/goliath/rack/params.rb
index 03d42939..59824423 100644
--- a/lib/goliath/rack/params.rb
+++ b/lib/goliath/rack/params.rb
@@ -14,66 +14,68 @@ module Rack
     #  use Goliath::Rack::Params
     #
     class Params
-      include Goliath::Rack::Validator
-
-      def initialize(app)
-        @app = app
-      end
-
-      def call(env)
-        Goliath::Rack::Validator.safely(env) do
-          env['params'] = retrieve_params(env)
-          @app.call(env)
-        end
-      end
-
-      def retrieve_params(env)
-        params = {}
-        params.merge!(::Rack::Utils.parse_nested_query(env['QUERY_STRING']))
+      module Parser
+        def retrieve_params(env)
+          params = env['params'] || {}
+          params.merge!(::Rack::Utils.parse_nested_query(env['QUERY_STRING']))
 
-        if env['rack.input']
-          post_params = ::Rack::Utils::Multipart.parse_multipart(env)
-          unless post_params
-            body = env['rack.input'].read
-            env['rack.input'].rewind
+          if env['rack.input']
+            post_params = ::Rack::Utils::Multipart.parse_multipart(env)
+            unless post_params
+              body = env['rack.input'].read
+              env['rack.input'].rewind
 
-            unless body.empty?
-              begin
-                post_params = case(env['CONTENT_TYPE'])
-                when URL_ENCODED then
-                  ::Rack::Utils.parse_nested_query(body)
-                when JSON_ENCODED then
-                  MultiJson.decode(body)
-                else
-                  {}
+              unless body.empty?
+                begin
+                  post_params = case(env['CONTENT_TYPE'])
+                  when URL_ENCODED then
+                    ::Rack::Utils.parse_nested_query(body)
+                  when JSON_ENCODED then
+                    MultiJson.decode(body)
+                  else
+                    {}
+                  end
+                rescue StandardError => e
+                  raise Goliath::Validation::BadRequestError, "Invalid parameters: #{e.class.to_s}"
                 end
-              rescue StandardError => e
-                raise Goliath::Validation::BadRequestError, "Invalid parameters: #{e.class.to_s}"
+              else
+                post_params = {}
               end
-            else
-              post_params = {}
             end
+
+            params.merge!(post_params)
           end
 
-          params.merge!(post_params)
+          indifferent_params(params)
         end
 
-        indifferent_params(params)
-      end
+        def indifferent_params(params)
+          params = indifferent_hash.merge(params)
+          params.each do |key, value|
+            next unless value.is_a?(Hash)
+            params[key] = indifferent_params(value)
+          end
+        end
 
-      def indifferent_params(params)
-        params = indifferent_hash.merge(params)
-        params.each do |key, value|
-          next unless value.is_a?(Hash)
-          params[key] = indifferent_params(value)
+        # Creates a Hash with indifferent access.
+        def indifferent_hash
+          Hash.new {|hash,key| hash[key.to_s] if Symbol === key }
         end
       end
 
-      # Creates a Hash with indifferent access.
-      def indifferent_hash
-        Hash.new {|hash,key| hash[key.to_s] if Symbol === key }
+      include Goliath::Rack::Validator
+      include Parser
+
+      def initialize(app)
+        @app = app
       end
 
+      def call(env)
+        Goliath::Rack::Validator.safely(env) do
+          env['params'] = retrieve_params(env)
+          @app.call(env)
+        end
+      end
     end
   end
 end
diff --git a/spec/integration/rack_routes_spec.rb b/spec/integration/rack_routes_spec.rb
index 67cda028..94e48139 100644
--- a/spec/integration/rack_routes_spec.rb
+++ b/spec/integration/rack_routes_spec.rb
@@ -34,10 +34,19 @@
     end
 
     it 'routes to the correct API using regex filters' do
+      with_api(RackRoutes) do
+        get_request({:path => '/98'}, err) do |c|
+          c.response_header.status.should == 200
+          c.response.should == 'number 98!'
+        end
+      end
+    end
+
+    it 'routes to the correct API referencing params in the body of the buidler' do
       with_api(RackRoutes) do
         get_request({:path => '/123123'}, err) do |c|
           c.response_header.status.should == 200
-          c.response.should == 'number 123123!'
+          c.response.should == 'big number 123123!'
         end
       end
     end