diff --git a/src/Illuminate/Database/Eloquent/Relations/MorphTo.php b/src/Illuminate/Database/Eloquent/Relations/MorphTo.php
index 1ea2ccc3cfb3..28867c7e4d90 100644
--- a/src/Illuminate/Database/Eloquent/Relations/MorphTo.php
+++ b/src/Illuminate/Database/Eloquent/Relations/MorphTo.php
@@ -120,7 +120,7 @@ protected function getResultsByType($type)
                             ->mergeConstraintsFrom($this->getQuery())
                             ->with(array_merge(
                                 $this->getQuery()->getEagerLoads(),
-                                $this->typedEagerLoads[get_class($instance)] ?? []
+                                (array) ($this->typedEagerLoads[get_class($instance)] ?? [])
                             ));
 
         return $query->whereIn(
@@ -266,9 +266,7 @@ public function getDictionary()
     /**
      * Specify which relations to load for a given morph type.
      *
-     * @param string $modelClass
      * @param array $with
-     *
      * @return \Illuminate\Database\Eloquent\Relations\MorphTo
      */
     public function withMorph(array $with)
diff --git a/tests/Integration/Database/EloquentMorphEagerLoadingTest.php b/tests/Integration/Database/EloquentMorphEagerLoadingTest.php
index 2e63143b88b0..b7ba197a6f75 100644
--- a/tests/Integration/Database/EloquentMorphEagerLoadingTest.php
+++ b/tests/Integration/Database/EloquentMorphEagerLoadingTest.php
@@ -50,7 +50,7 @@ public function test_with_morph_loading()
     {
         $comments = Comment::query()
             ->with(['commentable' => function (MorphTo $morphTo) {
-                $morphTo->withMorph([Post::class =>['user']]);
+                $morphTo->withMorph([Post::class => ['user']]);
             }])
             ->get();
 
@@ -58,6 +58,18 @@ public function test_with_morph_loading()
         $this->assertTrue($comments[0]->commentable->relationLoaded('user'));
         $this->assertTrue($comments[1]->relationLoaded('commentable'));
     }
+
+    public function test_with_morph_loading_with_single_relation()
+    {
+        $comments = Comment::query()
+            ->with(['commentable' => function (MorphTo $morphTo) {
+                $morphTo->withMorph([Post::class => 'user']);
+            }])
+            ->get();
+
+        $this->assertTrue($comments[0]->relationLoaded('commentable'));
+        $this->assertTrue($comments[0]->commentable->relationLoaded('user'));
+    }
 }
 
 class Comment extends Model