diff --git a/force-app/main/default/lwc/gantt_chart_resource/gantt_chart_resource.js b/force-app/main/default/lwc/gantt_chart_resource/gantt_chart_resource.js
index 184c8a1..4dd3233 100755
--- a/force-app/main/default/lwc/gantt_chart_resource/gantt_chart_resource.js
+++ b/force-app/main/default/lwc/gantt_chart_resource/gantt_chart_resource.js
@@ -237,6 +237,7 @@ export default class GanttChartResource extends LightningElement {
       };
 
       self.resource.allocationsByProject[projectId].forEach(allocation => {
+        allocation = {...allocation}; //clone immutable object
         allocation.class = self.calcClass(allocation);
         allocation.style = self.calcStyle(allocation);
         allocation.labelStyle = self.calcLabelStyle(allocation);