diff --git a/lib/api/v3/work_packages/schema/work_package_schema.rb b/lib/api/v3/work_packages/schema/work_package_schema.rb
index f67529763c..2f26a8b387 100644
--- a/lib/api/v3/work_packages/schema/work_package_schema.rb
+++ b/lib/api/v3/work_packages/schema/work_package_schema.rb
@@ -59,7 +59,7 @@ module API
           end
 
           def assignable_versions
-            @work_package.assignable_versions unless @work_package.nil?
+            @work_package.try(:assignable_versions)
           end
 
           def assignable_priorities