diff --git a/app/models/ci/job_artifact.rb b/app/models/ci/job_artifact.rb
index e6e7c7279f8..740d1c824f9 100644
--- a/app/models/ci/job_artifact.rb
+++ b/app/models/ci/job_artifact.rb
@@ -70,7 +70,7 @@ module Ci
     end
 
     def update_project_statistics_after_destroy
-      update_project_statistics(-self.size) if self.size
+      update_project_statistics(-self.size.to_i)
     end
 
     def update_project_statistics(difference)