diff --git a/src/Serializer/Traits/BreadcrumbSeralizerTrait.php b/src/Serializer/Traits/BreadcrumbSeralizerTrait.php
index 7fe10ce25..23e840380 100644
--- a/src/Serializer/Traits/BreadcrumbSeralizerTrait.php
+++ b/src/Serializer/Traits/BreadcrumbSeralizerTrait.php
@@ -20,7 +20,7 @@ trait BreadcrumbSeralizerTrait
      *     level: string,
      *     timestamp: float,
      *     message?: string,
-     *     data?: array<string, mixed>
+     *     data?: object
      * }
      */
     protected static function serializeBreadcrumb(Breadcrumb $breadcrumb): array
@@ -37,7 +37,7 @@ protected static function serializeBreadcrumb(Breadcrumb $breadcrumb): array
         }
 
         if (!empty($breadcrumb->getMetadata())) {
-            $result['data'] = $breadcrumb->getMetadata();
+            $result['data'] = (object) $breadcrumb->getMetadata();
         }
 
         return $result;
diff --git a/tests/Serializer/PayloadSerializerTest.php b/tests/Serializer/PayloadSerializerTest.php
index a3e8e5c08..9c294fa72 100644
--- a/tests/Serializer/PayloadSerializerTest.php
+++ b/tests/Serializer/PayloadSerializerTest.php
@@ -83,6 +83,7 @@ public static function serializeAsEnvelopeDataProvider(): iterable
         $event->setBreadcrumb([
             new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_USER, 'log'),
             new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_NAVIGATION, 'log', null, ['from' => '/login', 'to' => '/dashboard']),
+            new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'log', null, ['foo', 'bar']),
         ]);
 
         $event->setUser(UserDataBag::createFromArray([
@@ -169,7 +170,7 @@ public static function serializeAsEnvelopeDataProvider(): iterable
             <<<TEXT
 {"event_id":"fc9442f5aef34234bb22b9a615e30ccd","sent_at":"2020-08-18T22:47:15Z","dsn":"http:\/\/public@example.com\/sentry\/1","sdk":{"name":"sentry.php","version":"$sdkVersion"}}
 {"type":"event","content_type":"application\/json"}
-{"timestamp":1597790835,"platform":"php","sdk":{"name":"sentry.php","version":"$sdkVersion"},"start_timestamp":1597790835,"level":"error","logger":"app.php","transaction":"\/users\/<username>\/","server_name":"foo.example.com","release":"721e41770371db95eee98ca2707686226b993eda","environment":"production","fingerprint":["myrpc","POST","\/foo.bar"],"modules":{"my.module.name":"1.0"},"extra":{"my_key":1,"some_other_value":"foo bar"},"tags":{"ios_version":"4.0","context":"production"},"user":{"id":"unique_id","username":"my_user","email":"foo@example.com","ip_address":"127.0.0.1","segment":"my_segment"},"contexts":{"os":{"name":"Linux","version":"4.19.104-microsoft-standard","build":"#1 SMP Wed Feb 19 06:37:35 UTC 2020","kernel_version":"Linux 7944782cd697 4.19.104-microsoft-standard #1 SMP Wed Feb 19 06:37:35 UTC 2020 x86_64"},"runtime":{"name":"php","version":"7.4.3"},"electron":{"type":"runtime","name":"Electron","version":"4.0"}},"breadcrumbs":{"values":[{"type":"user","category":"log","level":"info","timestamp":1597790835},{"type":"navigation","category":"log","level":"info","timestamp":1597790835,"data":{"from":"\/login","to":"\/dashboard"}}]},"request":{"method":"POST","url":"http:\/\/absolute.uri\/foo","query_string":"query=foobar&page=2","data":{"foo":"bar"},"cookies":{"PHPSESSID":"298zf09hf012fh2"},"headers":{"content-type":"text\/html"},"env":{"REMOTE_ADDR":"127.0.0.1"}},"exception":{"values":[{"type":"Exception","value":"chained exception","stacktrace":{"frames":[{"filename":"file\/name.py","lineno":3,"in_app":true},{"filename":"file\/name.py","lineno":3,"in_app":false,"abs_path":"absolute\/file\/name.py","function":"myfunction","raw_function":"raw_function_name","pre_context":["def foo():","  my_var = 'foo'"],"context_line":"  raise ValueError()","post_context":["","def main():"],"vars":{"my_var":"value"}}]},"mechanism":{"type":"generic","handled":true,"data":{"code":123}}},{"type":"Exception","value":"initial exception"}]}}
+{"timestamp":1597790835,"platform":"php","sdk":{"name":"sentry.php","version":"$sdkVersion"},"start_timestamp":1597790835,"level":"error","logger":"app.php","transaction":"\/users\/<username>\/","server_name":"foo.example.com","release":"721e41770371db95eee98ca2707686226b993eda","environment":"production","fingerprint":["myrpc","POST","\/foo.bar"],"modules":{"my.module.name":"1.0"},"extra":{"my_key":1,"some_other_value":"foo bar"},"tags":{"ios_version":"4.0","context":"production"},"user":{"id":"unique_id","username":"my_user","email":"foo@example.com","ip_address":"127.0.0.1","segment":"my_segment"},"contexts":{"os":{"name":"Linux","version":"4.19.104-microsoft-standard","build":"#1 SMP Wed Feb 19 06:37:35 UTC 2020","kernel_version":"Linux 7944782cd697 4.19.104-microsoft-standard #1 SMP Wed Feb 19 06:37:35 UTC 2020 x86_64"},"runtime":{"name":"php","version":"7.4.3"},"electron":{"type":"runtime","name":"Electron","version":"4.0"}},"breadcrumbs":{"values":[{"type":"user","category":"log","level":"info","timestamp":1597790835},{"type":"navigation","category":"log","level":"info","timestamp":1597790835,"data":{"from":"\/login","to":"\/dashboard"}},{"type":"default","category":"log","level":"info","timestamp":1597790835,"data":{"0":"foo","1":"bar"}}]},"request":{"method":"POST","url":"http:\/\/absolute.uri\/foo","query_string":"query=foobar&page=2","data":{"foo":"bar"},"cookies":{"PHPSESSID":"298zf09hf012fh2"},"headers":{"content-type":"text\/html"},"env":{"REMOTE_ADDR":"127.0.0.1"}},"exception":{"values":[{"type":"Exception","value":"chained exception","stacktrace":{"frames":[{"filename":"file\/name.py","lineno":3,"in_app":true},{"filename":"file\/name.py","lineno":3,"in_app":false,"abs_path":"absolute\/file\/name.py","function":"myfunction","raw_function":"raw_function_name","pre_context":["def foo():","  my_var = 'foo'"],"context_line":"  raise ValueError()","post_context":["","def main():"],"vars":{"my_var":"value"}}]},"mechanism":{"type":"generic","handled":true,"data":{"code":123}}},{"type":"Exception","value":"initial exception"}]}}
 TEXT
         ];