diff --git a/packages/backend/src/core/activitypub/type.ts b/packages/backend/src/core/activitypub/type.ts
index 119a9d8ccb..08bd224700 100644
--- a/packages/backend/src/core/activitypub/type.ts
+++ b/packages/backend/src/core/activitypub/type.ts
@@ -56,10 +56,17 @@ export function getOneApId(value: ApObject): string {
 	return getApId(firstOne);
 }
 
+/**
+ * Minimal AP payload - just an object with optional ID.
+ */
+export interface ObjectWithId {
+	id?: string;
+}
+
 /**
  * Get ActivityStreams Object id
  */
-export function getApId(value: string | IObject | [string | IObject]): string {
+export function getApId(value: string | ObjectWithId | [string | ObjectWithId]): string {
 	// eslint-disable-next-line no-param-reassign
 	value = fromTuple(value);
 
@@ -71,7 +78,7 @@ export function getApId(value: string | IObject | [string | IObject]): string {
 /**
  * Get ActivityStreams Object id, or null if not present
  */
-export function getNullableApId(value: string | IObject | [string | IObject]): string | null {
+export function getNullableApId(value: string | ObjectWithId | [string | ObjectWithId]): string | null {
 	// eslint-disable-next-line no-param-reassign
 	value = fromTuple(value);