diff --git a/src/xyArray/xyArrayWeightedMerge.ts b/src/xyArray/xyArrayWeightedMerge.ts
index 60139d4c6..d0c336dda 100644
--- a/src/xyArray/xyArrayWeightedMerge.ts
+++ b/src/xyArray/xyArrayWeightedMerge.ts
@@ -20,7 +20,7 @@ export interface XYArrayWeightedMergeOptions {
 export function xyArrayWeightedMerge(
   data: DataXY[],
   options: XYArrayWeightedMergeOptions = {},
-): DataXY {
+): DataXY<number[]> {
   let { delta = 1 } = options;
   if (typeof delta === 'number') {
     const deltaNumber = delta;