diff --git a/superset-frontend/plugins/plugin-chart-echarts/src/utils/formatters.ts b/superset-frontend/plugins/plugin-chart-echarts/src/utils/formatters.ts
index 2c53abf3839..579a621abb3 100644
--- a/superset-frontend/plugins/plugin-chart-echarts/src/utils/formatters.ts
+++ b/superset-frontend/plugins/plugin-chart-echarts/src/utils/formatters.ts
@@ -88,7 +88,7 @@ export function getTooltipTimeFormatter(
 
 export function getXAxisFormatter(
   format?: string,
-): TimeFormatter | StringConstructor | undefined {
+): TimeFormatter | undefined {
   if (format === SMART_DATE_ID) {
     return getSmartDateFormatter();
   }
diff --git a/superset-frontend/plugins/plugin-chart-echarts/test/utils/formatters.test.ts b/superset-frontend/plugins/plugin-chart-echarts/test/utils/formatters.test.ts
index fb47deafa0b..df3ac5ddd28 100644
--- a/superset-frontend/plugins/plugin-chart-echarts/test/utils/formatters.test.ts
+++ b/superset-frontend/plugins/plugin-chart-echarts/test/utils/formatters.test.ts
@@ -74,9 +74,7 @@ describe('getXAxisFormatter', () => {
     expect(formatter).toEqual(expectedFormatter);
   });
 
-  it('should return String constructor as fallback', () => {
-    // This test verifies that the String constructor is returned
-    // Note: the current logic may not reach this case, but keeping for completeness
+  it('should return undefined for falsy values', () => {
     const formatter = getXAxisFormatter(null as any);
     expect(formatter).toBeUndefined();
   });