diff --git a/lib/swagger_rails/engine.rb b/lib/swagger_rails/engine.rb
index da55d0a..68d95d1 100644
--- a/lib/swagger_rails/engine.rb
+++ b/lib/swagger_rails/engine.rb
@@ -7,7 +7,9 @@ module SwaggerRails
     initializer 'swagger_rails.initialize' do |app|
       middleware.use SwaggerJson, SwaggerRails.config
 
-      app.config.assets.precompile += [ 'swagger-ui/*' ]
+      if app.config.respond_to?(:assets)
+        app.config.assets.precompile += [ 'swagger-ui/*' ]
+      end
     end
   end
 end