diff --git a/index.bs b/index.bs
index bad66c9bf..8bc636a80 100644
--- a/index.bs
+++ b/index.bs
@@ -1522,7 +1522,7 @@ that are returned to the caller when a new credential is created, or a new asser
     interface PublicKeyCredential : Credential {
         [SameObject] readonly attribute ArrayBuffer              rawId;
         [SameObject] readonly attribute AuthenticatorResponse    response;
-        [SameObject] readonly attribute DOMString?               authenticatorAttachment;
+        readonly attribute DOMString?                            authenticatorAttachment;
         AuthenticationExtensionsClientOutputs getClientExtensionResults();
         static Promise<boolean> isConditionalMediationAvailable();
         PublicKeyCredentialJSON toJSON();