diff --git a/src/index.ts b/src/index.ts
index fedd2fc..2d5683b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -144,7 +144,7 @@ export class ChartwerkScatterPod extends ChartwerkPod<ScatterData, ScatterOption
   }
 
   getSerieByIdx(idx: number): ScatterData | undefined {
-    return _.find(this.series.visibleSeries, serie => serie.idx = idx);
+    return _.find(this.series.visibleSeries, serie => serie.idx === idx);
   }
 
   getSeriesColorFromDataRow(values: number[], rowIdx: number): string {