diff --git a/frontend/benefit/handler/src/components/alterationHandling/AlterationCalculator.tsx b/frontend/benefit/handler/src/components/alterationHandling/AlterationCalculator.tsx
index d295682049..fce7663fd0 100644
--- a/frontend/benefit/handler/src/components/alterationHandling/AlterationCalculator.tsx
+++ b/frontend/benefit/handler/src/components/alterationHandling/AlterationCalculator.tsx
@@ -150,7 +150,8 @@ const AlterationCalculator = ({
             {
               start: rowStartDate,
               end: rowEndDate,
-            }
+            },
+            { inclusive: true }
           )
         ) {
           return sum;