diff --git a/app/models/work_package/exports/formatters/done_ratio.rb b/app/models/work_package/exports/formatters/done_ratio.rb
index 27ec3d5353d0..dd1a1d929636 100644
--- a/app/models/work_package/exports/formatters/done_ratio.rb
+++ b/app/models/work_package/exports/formatters/done_ratio.rb
@@ -34,7 +34,7 @@ def self.apply?(name, _export_format)
 
       def format(work_package, **)
         derived_done_ratio = work_package.derived_done_ratio
-        derived  = derived_done_ratio > 0 ? " · Σ #{derived_done_ratio}%" : ""
+        derived = derived_done_ratio&.positive? ? " · Σ #{derived_done_ratio}%" : ""
         "#{work_package.done_ratio}%#{derived}"
       end
     end