diff --git a/src/PostgREST/ApiRequest/Types.hs b/src/PostgREST/ApiRequest/Types.hs
index cbc1231ca..e419dae4a 100644
--- a/src/PostgREST/ApiRequest/Types.hs
+++ b/src/PostgREST/ApiRequest/Types.hs
@@ -71,13 +71,13 @@ data ApiRequestError
   | InvalidRpcMethod ByteString
   | LimitNoOrderError
   | NotFound
-  | NotToOne Text Text
   | NoRelBetween Text Text Text
   | NoRpc Text Text [Text] Bool MediaType Bool
   | NotEmbedded Text
   | ParseRequestError Text Text
   | PutRangeNotAllowedError
   | QueryParamError QPError
+  | RelatedOrderNotToOne Text Text
   | SpreadNotToOne Text Text
   | UnacceptableSchema [Text]
   | UnsupportedMethod ByteString
diff --git a/src/PostgREST/Error.hs b/src/PostgREST/Error.hs
index caad95b38..07accc74b 100644
--- a/src/PostgREST/Error.hs
+++ b/src/PostgREST/Error.hs
@@ -64,7 +64,6 @@ instance PgrstError ApiRequestError where
   status InvalidRpcMethod{}      = HTTP.status405
   status InvalidRange{}          = HTTP.status416
   status NotFound                = HTTP.status404
-  status NotToOne{}              = HTTP.status400
 
   status NoRelBetween{}          = HTTP.status400
   status NoRpc{}                 = HTTP.status404
@@ -72,6 +71,7 @@ instance PgrstError ApiRequestError where
   status ParseRequestError{}     = HTTP.status400
   status PutRangeNotAllowedError = HTTP.status400
   status QueryParamError{}       = HTTP.status400
+  status RelatedOrderNotToOne{}  = HTTP.status400
   status SpreadNotToOne{}        = HTTP.status400
   status UnacceptableSchema{}    = HTTP.status406
   status UnsupportedMethod{}     = HTTP.status405
@@ -154,10 +154,10 @@ instance JSON.ToJSON ApiRequestError where
     "details" .= JSON.Null,
     "hint"    .= JSON.Null]
 
-  toJSON (NotToOne origin target) = JSON.object [
+  toJSON (RelatedOrderNotToOne origin target) = JSON.object [
     "code"    .= ApiRequestErrorCode18,
-    "message" .= ("'" <> origin <> "' and '" <> target <> "' do not form a many-to-one or one-to-one relationship" :: Text),
-    "details" .= JSON.Null,
+    "message" .= ("A related order on '" <> target <> "' is not possible" :: Text),
+    "details" .= ("'" <> origin <> "' and '" <> target <> "' do not form a many-to-one or one-to-one relationship" :: Text),
     "hint"    .= JSON.Null]
 
   toJSON (SpreadNotToOne origin target) = JSON.object [
diff --git a/src/PostgREST/Plan.hs b/src/PostgREST/Plan.hs
index a79acace5..54c69f103 100644
--- a/src/PostgREST/Plan.hs
+++ b/src/PostgREST/Plan.hs
@@ -328,7 +328,7 @@ addRelatedOrders (Node rp@ReadPlan{order,from} forest) = do
               name    = fromMaybe relName relAlias in
           if isToOne == Just True
             then Right $ ot{otRelation=relAggAlias}
-            else Left $ NotToOne (qiName from) name
+            else Left $ RelatedOrderNotToOne (qiName from) name
         Nothing ->
           Left $ NotEmbedded otRelation
 
diff --git a/test/spec/Feature/Query/RelatedQueriesSpec.hs b/test/spec/Feature/Query/RelatedQueriesSpec.hs
index ddb35c377..0d3167415 100644
--- a/test/spec/Feature/Query/RelatedQueriesSpec.hs
+++ b/test/spec/Feature/Query/RelatedQueriesSpec.hs
@@ -107,17 +107,32 @@ spec =
 
     it "fails when is not a to-one relationship" $ do
       get "/clients?select=*,projects(*)&order=projects(id)" `shouldRespondWith`
-        [json|{"code":"PGRST118","details":null,"hint":null,"message":"'clients' and 'projects' do not form a many-to-one or one-to-one relationship"}|]
+        [json|{
+          "code":"PGRST118",
+          "details":"'clients' and 'projects' do not form a many-to-one or one-to-one relationship",
+          "hint":null,
+          "message":"A related order on 'projects' is not possible"
+        }|]
         { matchStatus  = 400
         , matchHeaders = [matchContentTypeJson]
         }
       get "/clients?select=*,pros:projects(*)&order=pros(id)" `shouldRespondWith`
-        [json|{"code":"PGRST118","details":null,"hint":null,"message":"'clients' and 'pros' do not form a many-to-one or one-to-one relationship"}|]
+        [json|{
+          "code":"PGRST118",
+          "details":"'clients' and 'pros' do not form a many-to-one or one-to-one relationship",
+          "hint":null,
+          "message":"A related order on 'pros' is not possible"
+        }|]
         { matchStatus  = 400
         , matchHeaders = [matchContentTypeJson]
         }
       get "/designers?select=id,computed_videogames(id)&order=computed_videogames(id).desc" `shouldRespondWith`
-        [json|{"code":"PGRST118","details":null,"hint":null,"message":"'designers' and 'computed_videogames' do not form a many-to-one or one-to-one relationship"}|]
+        [json|{
+          "code":"PGRST118",
+          "details":"'designers' and 'computed_videogames' do not form a many-to-one or one-to-one relationship",
+          "hint":null,
+          "message":"A related order on 'computed_videogames' is not possible"
+        }|]
         { matchStatus  = 400
         , matchHeaders = [matchContentTypeJson]
         }