# Probably i found a bug in zeppelin contracts

**URL:** <https://forum.openzeppelin.com/t/probably-i-found-a-bug-in-zeppelin-contracts/22059>\
**Category:** Smart Contracts\
**Created:** [January 2, 2022, 5:02pm UTC](https://forum.openzeppelin.com/t/probably-i-found-a-bug-in-zeppelin-contracts/22059 "2022-01-02T17:02:07Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![MeetEatMeat](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/meeteatmeat/32/9693_2.png) [@MeetEatMeat](https://forum.openzeppelin.com/u/MeetEatMeat)\
**Post date:** [January 2, 2022, 5:02pm UTC](https://forum.openzeppelin.com/t/probably-i-found-a-bug-in-zeppelin-contracts/22059/1 "2022-01-02T17:02:07Z")

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I got an error on several platforms with isContract() function which is a member of AddressUpgradeable. ERC721Upgradeable uses AddressUpgradeable for address. And when it uses "isContract" function each time causes error

 ![Снимок экрана 2022-01-02 в 21.57.23](https://us1.discourse-cdn.com/flex022/uploads/zeppelin/original/2X/3/3b27a72608dc985330d49bb05f10bc9a0c1b02a6.png)