diff --git a/src/state/chart_state.ts b/src/state/chart_state.ts
index f849e8f524..1b72616fbb 100644
--- a/src/state/chart_state.ts
+++ b/src/state/chart_state.ts
@@ -181,7 +181,7 @@ export interface PointerStates {
 /** @internal */
 export interface InteractionsState {
   pointer: PointerStates;
-  highlightedLegendItemKey: PrimitiveValue | null;
+  highlightedLegendItemKey: PrimitiveValue;
   highlightedLegendPath: LegendPath;
   deselectedDataSeries: SeriesIdentifier[];
 }