diff --git a/packages/x-charts/src/BarChart/formatter.ts b/packages/x-charts/src/BarChart/formatter.ts
index 2c7d571fb0772..e7cc322ad8142 100644
--- a/packages/x-charts/src/BarChart/formatter.ts
+++ b/packages/x-charts/src/BarChart/formatter.ts
@@ -86,9 +86,7 @@ const formatter: Formatter<'bar'> = (params, dataset) => {
   return {
     seriesOrder,
     stackingGroups,
-    series: defaultizeValueFormatter(completedSeries, (v) =>
-      v === null ? '' : v.toLocaleString(),
-    ),
+    series: defaultizeValueFormatter(completedSeries, (v) => (v == null ? '' : v.toLocaleString())),
   };
 };
 
diff --git a/packages/x-charts/src/LineChart/formatter.ts b/packages/x-charts/src/LineChart/formatter.ts
index 7734671d42053..d041eff126794 100644
--- a/packages/x-charts/src/LineChart/formatter.ts
+++ b/packages/x-charts/src/LineChart/formatter.ts
@@ -83,9 +83,7 @@ const formatter: Formatter<'line'> = (params, dataset) => {
   return {
     seriesOrder,
     stackingGroups,
-    series: defaultizeValueFormatter(completedSeries, (v) =>
-      v === null ? '' : v.toLocaleString(),
-    ),
+    series: defaultizeValueFormatter(completedSeries, (v) => (v == null ? '' : v.toLocaleString())),
   };
 };