diff --git a/src/UXClient/Components/LineChart/LineChart.ts b/src/UXClient/Components/LineChart/LineChart.ts
index 498124c..f4adcb0 100644
--- a/src/UXClient/Components/LineChart/LineChart.ts
+++ b/src/UXClient/Components/LineChart/LineChart.ts
@@ -1286,11 +1286,13 @@ class LineChart extends TemporalXAxisComponent {
                 aEO.swimLane = 0;
             });
             // consolidate horizontal markers
-            const horizontalMarkers = [];
-            Object.values(this.chartOptions.swimLaneOptions).forEach((lane) => {
-                horizontalMarkers.push(...lane.horizontalMarkers);
-            });
-            this.chartOptions.swimLaneOptions = {0: {yAxisType: this.chartOptions.yAxisState, horizontalMarkers: horizontalMarkers}};
+            if (this.chartOptions.swimLaneOptions) {
+                const horizontalMarkers = [];
+                Object.values(this.chartOptions.swimLaneOptions).forEach((lane) => {
+                    horizontalMarkers.push(...lane.horizontalMarkers);
+                });
+                this.chartOptions.swimLaneOptions = {0: {yAxisType: this.chartOptions.yAxisState, horizontalMarkers: horizontalMarkers}};
+            }
         } else {
             let minimumPresentSwimLane = this.aggregateExpressionOptions.reduce((currMin, aEO) => {
                 return Math.max(aEO.swimLane, currMin);