diff --git a/src/Illuminate/Database/Eloquent/Relations/Relation.php b/src/Illuminate/Database/Eloquent/Relations/Relation.php
index cba4ca2afed0..ca5dc6516d03 100755
--- a/src/Illuminate/Database/Eloquent/Relations/Relation.php
+++ b/src/Illuminate/Database/Eloquent/Relations/Relation.php
@@ -509,7 +509,7 @@ public static function getMorphedModel($alias)
      */
     public static function getMorphAlias(string $className)
     {
-        return array_flip(static::$morphMap)[$className] ?? null;
+        return array_search($className, static::$morphMap, strict: true) ?: $className;
     }
 
     /**
diff --git a/tests/Database/DatabaseEloquentRelationTest.php b/tests/Database/DatabaseEloquentRelationTest.php
index 47bd92710bcf..0fac8f8d3b7f 100755
--- a/tests/Database/DatabaseEloquentRelationTest.php
+++ b/tests/Database/DatabaseEloquentRelationTest.php
@@ -239,8 +239,8 @@ public function testGetMorphAlias()
     {
         Relation::morphMap(['user' => 'App\User']);
 
-        $this->assertEquals('user', Relation::getMorphAlias('App\User'));
-        $this->assertNull(Relation::getMorphAlias('Does\Not\Exist'));
+        $this->assertSame('user', Relation::getMorphAlias('App\User'));
+        $this->assertSame('Does\Not\Exist', Relation::getMorphAlias('Does\Not\Exist'));
     }
 
     public function testWithoutRelations()