diff --git a/activitypub.py b/activitypub.py
index 9e1b565..9c1a78a 100644
--- a/activitypub.py
+++ b/activitypub.py
@@ -494,8 +494,8 @@ def postprocess_as2(activity, orig_obj=None, wrap=True):
 
     Args:
       activity (dict): AS2 object or activity
-      orig_obj (dict): AS2 object, optional. The target of activity's ``inReplyTo`` or
-        ``Like``/``Announce``/etc object, if any.
+      orig_obj (dict): AS2 object, optional. The target of activity's
+        ``inReplyTo`` or ``Like``/``Announce``/etc object, if any.
       wrap (bool): whether to wrap ``id``, ``url``, ``object``, ``actor``, and
        ``attributedTo``
     """
@@ -524,12 +524,15 @@ def postprocess_as2(activity, orig_obj=None, wrap=True):
             })
         return activity
 
-    if wrap:
-        for field in 'actor', 'attributedTo':
-            activity[field] = [postprocess_as2_actor(actor, wrap=wrap)
-                               for actor in util.get_list(activity, field)]
-            if len(activity[field]) == 1:
-                activity[field] = activity[field][0]
+    # actors. wrap in our domain if necessary, then compact to just string id
+    # for compatibility, since many other AP implementations choke on objects.
+    # https://github.com/snarfed/bridgy-fed/issues/658
+    for field in 'actor', 'attributedTo', 'author':
+        actors = as1.get_objects(activity, field)
+        if wrap:
+            actors = [postprocess_as2_actor(actor, wrap=wrap) for actor in actors]
+        ids = [a['id'] for a in actors if a.get('id')]
+        activity[field] = ids[0] if len(ids) == 1 else ids
 
     # inReplyTo: singly valued, prefer id over url
     # TODO: ignore orig_obj, do for all inReplyTo
diff --git a/tests/test_activitypub.py b/tests/test_activitypub.py
index bebc645..a2f9f6e 100644
--- a/tests/test_activitypub.py
+++ b/tests/test_activitypub.py
@@ -224,7 +224,10 @@ ACCEPT = {
     'id': 'http://localhost/user.com/followers#accept-https://mas.to/6d1a',
     'actor': 'http://localhost/user.com',
     'object': {
-        **ACCEPT_FOLLOW,
+        'type': 'Follow',
+        'id': 'https://mas.to/6d1a',
+        'object': 'http://localhost/user.com',
+        'actor': 'https://mas.to/users/swentel',
         'url': 'https://mas.to/users/swentel#followed-https://user.com/',
         'to': ['https://www.w3.org/ns/activitystreams#Public'],
     },
@@ -1635,33 +1638,17 @@ class ActivityPubUtilsTest(TestCase):
             'image': [{'url': 'http://r/foo'}, {'url': 'http://r/bar'}],
         }))
 
-    def test_postprocess_as2_actor_attributedTo(self):
+    def test_postprocess_as2_actor_attributedTo_author(self):
         g.user = Fake(id='site')
         self.assert_equals({
-            'actor': {
-                'id': 'baj',
-                'preferredUsername': 'site',
-                'url': 'http://localhost/r/site',
-                'inbox': 'https://fa.brid.gy/ap/site/inbox',
-                'outbox': 'https://fa.brid.gy/ap/site/outbox',
-            },
-            'attributedTo': [{
-                'id': 'bar',
-                'preferredUsername': 'site',
-                'url': 'http://localhost/r/site',
-                'inbox': 'https://fa.brid.gy/ap/site/inbox',
-                'outbox': 'https://fa.brid.gy/ap/site/outbox',
-            }, {
-                'id': 'baz',
-                'preferredUsername': 'site',
-                'url': 'http://localhost/r/site',
-                'inbox': 'https://fa.brid.gy/ap/site/inbox',
-                'outbox': 'https://fa.brid.gy/ap/site/outbox',
-            }],
+            'actor': 'baj',
+            'attributedTo': ['bar', 'baz'],
+            'author': 'biff',
             'to': [as2.PUBLIC_AUDIENCE],
         }, postprocess_as2({
             'attributedTo': [{'id': 'bar'}, {'id': 'baz'}],
             'actor': {'id': 'baj'},
+            'author': {'id': 'biff'},
         }))
 
     def test_postprocess_as2_note(self):
diff --git a/tests/test_redirect.py b/tests/test_redirect.py
index 1985885..ea8b03e 100644
--- a/tests/test_redirect.py
+++ b/tests/test_redirect.py
@@ -23,7 +23,7 @@ from .test_web import (
 
 REPOST_AS2 = {
     **REPOST_AS2,
-    'actor': ACTOR_AS2,
+    'actor': 'http://localhost/user.com',
 }
 del REPOST_AS2['cc']
 
diff --git a/tests/test_web.py b/tests/test_web.py
index 649fe74..9b3e9e5 100644
--- a/tests/test_web.py
+++ b/tests/test_web.py
@@ -251,7 +251,7 @@ AS2_CREATE = {
             'https://mas.to/recipient',
             as2.PUBLIC_AUDIENCE,
         ],
-        'attributedTo': ACTOR_AS2,
+        'attributedTo': 'http://localhost/user.com',
         'tag': [{
             'type': 'Mention',
             'href': 'https://mas.to/author',
@@ -344,7 +344,7 @@ NOTE_AS2 = {
     'type': 'Note',
     'id': 'http://localhost/r/https://user.com/post',
     'url': 'http://localhost/r/https://user.com/post',
-    'attributedTo': ACTOR_AS2,
+    'attributedTo': 'http://localhost/user.com',
     'name': 'hello i am a post',
     'content': 'hello i am a post',
     'to': [as2.PUBLIC_AUDIENCE],