diff --git a/packages/builders/__tests__/messages/fileBody.test.ts b/packages/builders/__tests__/messages/fileBody.test.ts
index 4af96a382..3f46707e0 100644
--- a/packages/builders/__tests__/messages/fileBody.test.ts
+++ b/packages/builders/__tests__/messages/fileBody.test.ts
@@ -24,6 +24,17 @@ test('AttachmentBuilder stores and exposes file data', () => {
 	expect(attachment.getRawFile()).toBe(undefined);
 });
 
+test('AttachmentBuilder handles 0 as a valid id', () => {
+	const data = Buffer.from('test data');
+	const attachment = new AttachmentBuilder().setId(0).setFilename('test.txt').setFileData(data);
+
+	expect(attachment.getRawFile()).toStrictEqual({
+		data,
+		key: 'files[0]',
+		name: 'test.txt',
+	});
+});
+
 test('MessageBuilder.toFileBody returns JSON body and files', () => {
 	const msg = new MessageBuilder().setContent('here is a file').addAttachments(
 		new AttachmentBuilder()
diff --git a/packages/builders/src/messages/Attachment.ts b/packages/builders/src/messages/Attachment.ts
index 4e12e9d21..0c9b2494c 100644
--- a/packages/builders/src/messages/Attachment.ts
+++ b/packages/builders/src/messages/Attachment.ts
@@ -153,7 +153,7 @@ export class AttachmentBuilder implements JSONEncodable<RESTAPIAttachment> {
 		return {
 			...this.fileData,
 			name: this.data.filename,
-			key: this.data.id ? `files[${this.data.id}]` : undefined,
+			key: this.data.id === undefined ? undefined : `files[${this.data.id}]`,
 		};
 	}