diff --git a/src/common/legend.ts b/src/common/legend.ts
index 416d3d0885..73784c3da5 100644
--- a/src/common/legend.ts
+++ b/src/common/legend.ts
@@ -24,7 +24,7 @@ import { CategoryKey, CategoryLabel } from './category';
 import { SeriesIdentifier } from './series_id';
 
 /** @internal */
-export type LegendItemChildId = CategoryKey | number;
+export type LegendItemChildId = CategoryKey;
 
 /** @internal */
 export type LegendItem = {