# Switch to Composer: "Return type of SendGrid\\ReplyTo::jsonSerialize()"

**URL:** <https://forum.mautic.org/t/switch-to-composer-return-type-of-sendgrid-replyto-jsonserialize/27274>\
**Category:** Product Support\
**Tags:** mautic-4\
**Created:** [March 6, 2023, 7:31pm UTC](https://forum.mautic.org/t/switch-to-composer-return-type-of-sendgrid-replyto-jsonserialize/27274 "2023-03-06T19:31:56Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mcdiver](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/mcdiver/32/6618_2.png) [@mcdiver](https://forum.mautic.org/u/mcdiver)\
**Post date:** [March 6, 2023, 7:31pm UTC](https://forum.mautic.org/t/switch-to-composer-return-type-of-sendgrid-replyto-jsonserialize/27274/1 "2023-03-06T19:31:56Z")

</div>

**Your software**  
My Mautic version is: 4.4.6  
My PHP version is: 7.4.33  
My Database type and version is: MySQL 8.0.32

**Your problem**  
My problem is: For activating the Marketplace, I am trying to activate the composer with this explanation: [How to Switch to Composer](https://docs.mautic.org/en/setup/switch-to-composer)  
While executing this command (`composer create-project mautic/recommended-project:^4 html-new --no-interaction`) the following error is shown

These errors are showing in the log: “_Deprecated: Return type of SendGrid\ReplyTo::jsonSerialize() should either be compatible with JsonSerializable::jsonSerialize(): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /vendor/sendgrid/sendgrid/lib/helpers/mail/Mail.php on line 77_”

Steps I have tried to fix the problem: I tried to edit the Mail.php, but to be honest, as a rookie on php I have not been succesfull.

Thank you for some hints, about what I am doing wrong.