diff --git a/packages/rum-core/src/domain/assembly.ts b/packages/rum-core/src/domain/assembly.ts
index 68641e9701..dfaf268a7a 100644
--- a/packages/rum-core/src/domain/assembly.ts
+++ b/packages/rum-core/src/domain/assembly.ts
@@ -100,6 +100,7 @@ export function startRumAssembly(
       ...ROOT_MODIFIABLE_FIELD_PATHS,
     },
     [RumEventType.LONG_TASK]: {
+      'long_task.scripts[].source_url': 'string',
       ...USER_CUSTOMIZABLE_FIELD_PATHS,
       ...VIEW_MODIFIABLE_FIELD_PATHS,
     },