diff --git a/lib/sprockets/railtie.rb b/lib/sprockets/railtie.rb
index 7058a19a..5f579e9c 100644
--- a/lib/sprockets/railtie.rb
+++ b/lib/sprockets/railtie.rb
@@ -222,7 +222,7 @@ def self.build_manifest(app)
       if config.assets.compile
         app.assets = self.build_environment(app, true)
         app.routes.prepend do
-          mount app.assets => config.assets.prefix
+          mount app.assets, at: config.assets.prefix
         end
       end