diff --git a/lib/ontologies_linked_data/serializers/json.rb b/lib/ontologies_linked_data/serializers/json.rb
index 59f54a92..de622944 100644
--- a/lib/ontologies_linked_data/serializers/json.rb
+++ b/lib/ontologies_linked_data/serializers/json.rb
@@ -51,7 +51,7 @@ def self.type(current_cls, hashed_obj)
           proc = hashed_obj
         end
 
-        collection = hashed_obj.collection
+        collection = hashed_obj.respond_to?(:collection) ? hashed_obj.collection : nil
         if collection
           proc.type_uri(collection).to_s
         else