diff --git a/source/frontend/src/features/mapSideBar/property/tabs/propertyDetailsManagement/activity/edit/validation.ts b/source/frontend/src/features/mapSideBar/property/tabs/propertyDetailsManagement/activity/edit/validation.ts
index 5209c4197c..aef2b4003c 100644
--- a/source/frontend/src/features/mapSideBar/property/tabs/propertyDetailsManagement/activity/edit/validation.ts
+++ b/source/frontend/src/features/mapSideBar/property/tabs/propertyDetailsManagement/activity/edit/validation.ts
@@ -14,7 +14,9 @@ export const PropertyActivityEditFormYupSchema = Yup.object().shape({
     .required('Description is required')
     .max(2000, 'Description must be at most 2000 characters'),
 
-  requestedSource: Yup.string().max(2000, 'Requested source must be at most 2000 characters'),
+  requestedSource: Yup.string()
+    .nullable()
+    .max(2000, 'Requested source must be at most 2000 characters'),
 
   invoices: Yup.array().of(
     Yup.object().shape({