diff --git a/forms/qae_form_builder/matrix_question.rb b/forms/qae_form_builder/matrix_question.rb
index a400b1fc55..f168ba0158 100644
--- a/forms/qae_form_builder/matrix_question.rb
+++ b/forms/qae_form_builder/matrix_question.rb
@@ -101,6 +101,7 @@ def calculate_proportion(question_key, answers, x_heading, y_heading)
       else
         disadvantaged = answers["#{question_key}_#{x_heading}_total_disadvantaged"].to_f
       end
+      disadvantaged ||= 0
       total = answers["#{question_key}_#{x_heading}_calculated_total"].to_f
       proportion = (disadvantaged.to_f / total * 100).round(2)
       answers["#{question_key}_#{x_heading}_calculated_proportion"] = proportion