diff --git a/src/Vervis/Web/Actor.hs b/src/Vervis/Web/Actor.hs
index 1bfe0a9..e2306a1 100644
--- a/src/Vervis/Web/Actor.hs
+++ b/src/Vervis/Web/Actor.hs
@@ -65,7 +65,7 @@ import Yesod.Persist.Core
 import qualified Data.ByteString.Char8 as BC (unpack)
 import qualified Data.HashMap.Strict as M
 import qualified Data.Text as T
-import qualified Data.Text.Lazy as TL (toStrict)
+import qualified Data.Text.Lazy as TL
 import qualified Data.Vector as V
 import qualified Database.Esqueleto as E
 
@@ -88,6 +88,8 @@ import Data.Time.Clock.Local
 import Database.Persist.Local
 import Yesod.Persist.Local
 
+import qualified Data.Aeson.Encode.Pretty.ToEncoding as P
+
 import Vervis.ActivityPub
 import Vervis.ActorKey
 import Vervis.API
@@ -117,7 +119,10 @@ objectSummary o =
 objectId o =
     case M.lookup "id" o <|> M.lookup "@id" o of
         Just (String t) | not (T.null t) -> t
-        _ -> error "'id' field not found"
+        _ ->
+            error $
+                "'id' field not found" ++
+                TL.unpack (P.encodePrettyToLazyText o)
 
 getInbox here actor hash = do
     key <- decodeKeyHashid404 hash