diff --git a/src/lib/features/release-plans/release-plan-milestone-store.ts b/src/lib/features/release-plans/release-plan-milestone-store.ts
index 7dee7bf2ce..b81ee79ef3 100644
--- a/src/lib/features/release-plans/release-plan-milestone-store.ts
+++ b/src/lib/features/release-plans/release-plan-milestone-store.ts
@@ -16,7 +16,10 @@ const fromRow = (row: any): ReleasePlanMilestone => {
     };
 };
 
-export type ReleasePlanMilestoneWriteModel = Omit<ReleasePlanMilestone, 'id'>;
+export type ReleasePlanMilestoneWriteModel = Omit<
+    ReleasePlanMilestone,
+    'id' | 'startedAt' | 'transitionCondition'
+>;
 
 export class ReleasePlanMilestoneStore extends CRUDStore<
     ReleasePlanMilestone,
diff --git a/src/lib/features/release-plans/release-plan-milestone.ts b/src/lib/features/release-plans/release-plan-milestone.ts
index ad1a47e66a..7f677085f2 100644
--- a/src/lib/features/release-plans/release-plan-milestone.ts
+++ b/src/lib/features/release-plans/release-plan-milestone.ts
@@ -5,7 +5,7 @@ export interface ReleasePlanMilestone {
     name: string;
     sortOrder: number;
     releasePlanDefinitionId: string;
-    startedAt?: Date;
+    startedAt?: string;
     transitionCondition?: object;
     strategies?: ReleasePlanMilestoneStrategy[];
 }