diff --git a/lib/grape-active_model_serializers/formatter.rb b/lib/grape-active_model_serializers/formatter.rb
index 067ced1..1b3514d 100644
--- a/lib/grape-active_model_serializers/formatter.rb
+++ b/lib/grape-active_model_serializers/formatter.rb
@@ -6,7 +6,7 @@ module Grape
           serializer = fetch_serializer(resource, env)
 
           if serializer
-            serializer.to_json
+            ::ActiveModelSerializers::Adapter.create(serializer).to_json
           else
             Grape::Formatter::Json.call resource, env
           end