Example of the error

app/Http/Controllers/TheController.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use Illuminate\Http\Request;
+use App\TheRelationModel;
+use App\TheModel;
+
+class TheController extends Controller
+{
+    public function index()
+    {
+        $theModel = TheModel::where(['name' => 'foo'])->first();
+        abort_if(!$theModel, 404);
+
+        $theRelation = $theModel->theRelation()->where(['name' => 'bar'])->first();
+        abort_if(!$theRelation, 404);
+    }
+}

app/TheModel.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace App;
+
+use Illuminate\Database\Eloquent\Model;
+
+class TheModel extends Model
+{
+    public function theRelation()
+    {
+        return $this->hasOne(TheRelationModel::class);
+    }
+}

app/TheRelationModel.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace App;
+
+use Illuminate\Database\Eloquent\Model;
+
+class TheRelationModel extends Model
+{
+    public function theModel()
+    {
+        return $this->belongsTo(TheModel::class);
+    }
+}