diff --git a/.changeset/cost-insights-two-crabs-evolve.md b/.changeset/cost-insights-two-crabs-evolve.md
new file mode 100644
index 0000000000..8a932ea59c
--- /dev/null
+++ b/.changeset/cost-insights-two-crabs-evolve.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-cost-insights': patch
+---
+
+Fixed generation of sample data in the example Cost Insights client
diff --git a/plugins/cost-insights/src/testUtils/testUtils.ts b/plugins/cost-insights/src/testUtils/testUtils.ts
index 2c6f6b5ef2..e0ed1aa933 100644
--- a/plugins/cost-insights/src/testUtils/testUtils.ts
+++ b/plugins/cost-insights/src/testUtils/testUtils.ts
@@ -61,7 +61,7 @@ export function aggregationFor(
   const days = DateTime.fromISO(endDate).diff(
     DateTime.fromISO(inclusiveStartDateOf(duration, inclusiveEndDate)),
     'days',
-  );
+  ).days;
 
   function nextDelta(): number {
     const varianceFromBaseline = 0.15;