diff --git a/app/builders/learning_object_builder.rb b/app/builders/learning_object_builder.rb
index 67327f045b4a873f4b6ef2c940a861c53b72d997..b42a03ffb18319850c0c0839de2c0b71152d0d7f 100644
--- a/app/builders/learning_object_builder.rb
+++ b/app/builders/learning_object_builder.rb
@@ -27,7 +27,7 @@ class LearningObjectBuilder
           id: args['@rid'],
           name: args['name'],
           description: args['description'],
-          thumbnail: args['thumbnail'],
+          thumbnail: (args['thumbnail'] or ''),
           id_dspace: args['id_dspace'],
           type: args['type'],
           bitstreams: args['bitstreams'],