diff --git a/packages/backend/src/models/json-schema/user.ts b/packages/backend/src/models/json-schema/user.ts
index 9c88a078c0..dfefcd96f2 100644
--- a/packages/backend/src/models/json-schema/user.ts
+++ b/packages/backend/src/models/json-schema/user.ts
@@ -591,7 +591,7 @@ export const packedMeDetailedOnlySchema = {
 		},
 		mutedInstances: {
 			type: 'array',
-			nullable: true, optional: false,
+			nullable: false, optional: false,
 			items: {
 				type: 'string',
 				nullable: false, optional: false,