diff --git a/catalog/apis.py b/catalog/apis.py
index 1c9a7e77..8585a3fc 100644
--- a/catalog/apis.py
+++ b/catalog/apis.py
@@ -266,7 +266,6 @@ def get_book(request, uuid: str, response: HttpResponse):
 @paginate(PageNumberPagination)
 def get_sibling_editions_for_book(request, uuid: str, response: HttpResponse):
     i = _get_item(Edition, uuid, response)
-    print(i)
     if not isinstance(i, Edition):
         return Edition.objects.none()
     return i.sibling_items
diff --git a/catalog/collection/models.py b/catalog/collection/models.py
index b5da4902..7083851a 100644
--- a/catalog/collection/models.py
+++ b/catalog/collection/models.py
@@ -12,7 +12,7 @@ class Collection(Item):
 
     @property
     def url(self):
-        return self.journal_item.url if self.journal_item else super().url
+        return self.journal_item.url if hasattr(self, "journal_item") else super().url
 
     @property
     def owner_id(self):
diff --git a/catalog/common/sites.py b/catalog/common/sites.py
index 5188eb22..7b20efa7 100644
--- a/catalog/common/sites.py
+++ b/catalog/common/sites.py
@@ -261,6 +261,7 @@ class AbstractSite:
             p.save()
             if p.item:
                 p.item.merge_data_from_external_resources(ignore_existing_content)
+                p.item.ap_object  # validate
                 p.item.save()
                 self.scrape_additional_data()
         if auto_link:
diff --git a/catalog/sites/fedi.py b/catalog/sites/fedi.py
index d594dd8a..ee2c8728 100644
--- a/catalog/sites/fedi.py
+++ b/catalog/sites/fedi.py
@@ -1,3 +1,4 @@
+import re
 from urllib.parse import quote_plus, urlparse
 
 import httpx
@@ -68,7 +69,9 @@ class FediverseInstance(AbstractSite):
     @classmethod
     def url_to_id(cls, url: str):
         u = url.split("://", 1)[1].split("?", 1)[0].split("/", 1)
-        return "https://" + u[0].lower() + "/" + u[1]
+        return "https://" + u[0].lower() + "/" + re.sub("^api/", "", u[1])
+        # return "https://" + u[0].lower() + "/" + u[1]
+        # FIXME re.sub(...) should be removed after all peers in network upgrade to 0.11.4.9+
 
     @classmethod
     def validate_url_fallback(cls, url: str):
diff --git a/catalog/views.py b/catalog/views.py
index ebf30cb8..44d7e01c 100644
--- a/catalog/views.py
+++ b/catalog/views.py
@@ -1,7 +1,7 @@
 from django.contrib.auth.decorators import login_required
 from django.core.cache import cache
 from django.db.models import Count
-from django.http import Http404
+from django.http import Http404, JsonResponse
 from django.shortcuts import get_object_or_404, redirect, render
 from django.urls import reverse
 from django.utils import timezone
@@ -82,7 +82,7 @@ def retrieve(request, item_path, item_uuid):
     if not skipcheck and item.is_deleted:
         raise Http404(_("Item no longer exists"))
     if request.headers.get("Accept", "").endswith("json"):
-        return redirect(item.api_url)
+        return JsonResponse(item.ap_object)
     focus_item = None
     if request.GET.get("focus"):
         focus_item = get_object_or_404(
diff --git a/common/views.py b/common/views.py
index c6e91663..3334a293 100644
--- a/common/views.py
+++ b/common/views.py
@@ -81,23 +81,35 @@ def nodeinfo2(request):
     )
 
 
+def _is_json_request(request) -> bool:
+    return request.headers.get("HTTP_ACCEPT", "").endswith("json")
+
+
 def error_400(request, exception=None):
     if isinstance(exception, DisallowedHost):
         url = settings.SITE_INFO["site_url"] + request.get_full_path()
         return redirect(url, permanent=True)
+    if _is_json_request(request):
+        return JsonResponse({"error": "invalid request"}, status=400)
     return render(request, "400.html", status=400, context={"exception": exception})
 
 
 def error_403(request, exception=None):
+    if _is_json_request(request):
+        return JsonResponse({"error": "forbidden"}, status=403)
     return render(request, "403.html", status=403, context={"exception": exception})
 
 
 def error_404(request, exception=None):
+    if _is_json_request(request):
+        return JsonResponse({"error": "not found"}, status=404)
     request.session.pop("next_url", None)
     return render(request, "404.html", status=404, context={"exception": exception})
 
 
 def error_500(request, exception=None):
+    if _is_json_request(request):
+        return JsonResponse({"error": "something wrong"}, status=500)
     return render(request, "500.html", status=500, context={"exception": exception})