diff --git a/lib/omniauth/strategy.rb b/lib/omniauth/strategy.rb
index cd565da..7686543 100644
--- a/lib/omniauth/strategy.rb
+++ b/lib/omniauth/strategy.rb
@@ -226,11 +226,19 @@ module OmniAuth
     end
 
     def on_request_path?
-      on_path?(request_path)
+      if options.request_path.respond_to?(:call)
+        options.request_path.call(env)
+      else
+        on_path?(request_path)
+      end
     end
 
     def on_callback_path?
-      on_path?(callback_path)
+      if options.callback_path.respond_to?(:call)
+        options.callback_path.call(env)
+      else
+        on_path?(callback_path)
+      end
     end
 
     def on_path?(path)
@@ -350,12 +358,22 @@ module OmniAuth
       options[:path_prefix] || OmniAuth.config.path_prefix
     end
 
+    def custom_path(kind)
+      if options[kind].respond_to?(:call)
+        result = options[kind].call(env) 
+        return nil unless result.is_a?(String)
+        result
+      else
+        options[kind]
+      end
+    end
+
     def request_path
-      options[:request_path] || "#{path_prefix}/#{name}"
+      options[:request_path].is_a?(String) ? options[:request_path] : "#{path_prefix}/#{name}"
     end
 
     def callback_path
-      options[:callback_path] || "#{path_prefix}/#{name}/callback"
+      options[:callback_path].is_a?(String) ? options[:callback_path] : (custom_path(:request_path) || "#{path_prefix}/#{name}/callback")
     end
 
     def setup_path
diff --git a/spec/omniauth/strategy_spec.rb b/spec/omniauth/strategy_spec.rb
index 2d3a740..a1b0b53 100644
--- a/spec/omniauth/strategy_spec.rb
+++ b/spec/omniauth/strategy_spec.rb
@@ -346,6 +346,23 @@ describe OmniAuth::Strategy do
       end
     end
 
+    context 'dynamic paths' do
+      it 'should run the request phase if the custom request path evaluator is truthy' do
+        @options = {:request_path => lambda{|env| true}}
+        lambda{ strategy.call(make_env('/asoufibasfi')) }.should raise_error("Request Phase")
+      end
+
+      it 'should run the callback phase if the custom callback path evaluator is truthy' do
+        @options = {:callback_path => lambda{|env| true}}
+        lambda{ strategy.call(make_env('/asoufiasod')) }.should raise_error("Callback Phase")
+      end
+
+      it 'should provide a custom callback path if request_path evals to a string' do
+        strategy_instance = fresh_strategy.new(nil, :request_path => lambda{|env| "/auth/boo/callback/22" })
+        strategy_instance.callback_path.should == '/auth/boo/callback/22'
+      end      
+    end
+
     context 'custom paths' do
       it 'should use a custom request_path if one is provided' do
         @options = {:request_path => '/awesome'}