diff --git a/packages/backend/src/misc/is-pure-renote.ts b/packages/backend/src/misc/is-pure-renote.ts
new file mode 100644
index 0000000000..a6faadd7db
--- /dev/null
+++ b/packages/backend/src/misc/is-pure-renote.ts
@@ -0,0 +1,10 @@
+import type { MiNote } from '@/models/Note.js';
+
+export function isPureRenote(note: MiNote): boolean {
+	if (!note.renoteId) return false;
+
+	if (note.text) return false; // it's quoted with text
+	if (note.fileIds.length !== 0) return false; // it's quoted with files
+	if (note.hasPoll) return false; // it's quoted with poll
+	return true;
+}
diff --git a/packages/backend/src/server/api/endpoints/notes/create.ts b/packages/backend/src/server/api/endpoints/notes/create.ts
index 52a16dde55..649068fb20 100644
--- a/packages/backend/src/server/api/endpoints/notes/create.ts
+++ b/packages/backend/src/server/api/endpoints/notes/create.ts
@@ -17,6 +17,7 @@ import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
 import { NoteCreateService } from '@/core/NoteCreateService.js';
 import { DI } from '@/di-symbols.js';
 import { ApiError } from '../../error.js';
+import { isPureRenote } from '@/misc/is-pure-renote.js';
 
 export const meta = {
 	tags: ['notes'],
@@ -214,15 +215,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}
 			}
 
-			function isPureRenote(note: MiNote): boolean {
-				if (!note.renoteId) return false;
-
-				if (note.text) return false; // it's quoted with text
-				if (note.fileIds.length !== 0) return false; // it's quoted with files
-				if (note.hasPoll) return false; // it's quoted with poll
-				return true;
-			}
-
 			let renote: MiNote | null = null;
 			if (ps.renoteId != null) {
 				// Fetch renote to note