# Erc721 contract

**URL:** <https://forum.openzeppelin.com/t/erc721-contract/459>\
**Category:** Contracts\
**Created:** [March 27, 2019, 6:27pm UTC](https://forum.openzeppelin.com/t/erc721-contract/459 "2019-03-27T18:27:10Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![mssmx](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/mssmx/32/345_2.png) [@mssmx](https://forum.openzeppelin.com/u/mssmx)\
**Post date:** [March 27, 2019, 6:27pm UTC](https://forum.openzeppelin.com/t/erc721-contract/459/1 "2019-03-27T18:27:11Z")

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sorry for this simple question. I was implementing as a test a erc721 contract. I’ve seen that example on your site does not work fine with new version of openzeppelin. can someone light me on what changes are needed?  
thanks

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**Author:** ![nventuro](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/nventuro/32/8_2.png) [@nventuro](https://forum.openzeppelin.com/u/nventuro)\
**Post date:** [March 27, 2019, 8:20pm UTC](https://forum.openzeppelin.com/t/erc721-contract/459/2 "2019-03-27T20:20:34Z")

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Hello @mssmx! Could you share some information as to what it is you intend to do, and the errors you’re encountering?

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**Author:** ![mssmx](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/mssmx/32/345_2.png) [@mssmx](https://forum.openzeppelin.com/u/mssmx)\
**Post date:** [March 30, 2019, 6:41pm UTC](https://forum.openzeppelin.com/t/erc721-contract/459/3 "2019-03-30T18:41:22Z")

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sorry for confusion. i was testing doggo [https://docs.openzeppelin.org/docs/learn-about-tokens.html](https://docs.openzeppelin.org/docs/learn-about-tokens.html) with truffle. i got this error when compiling  
Error: Identifier not found or not unique.  
i am using truffle last version and openzeppelin last version.  
where am i wrong?

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**Author:** ![nventuro](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/nventuro/32/8_2.png) [@nventuro](https://forum.openzeppelin.com/u/nventuro)\
**Post date:** [April 1, 2019, 3:47pm UTC](https://forum.openzeppelin.com/t/erc721-contract/459/4 "2019-04-01T15:47:46Z")

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> [@mssmx](#):
>
> Error: Identifier not found or not unique.

Hmm, the guide may be outdated if you get that. Could you please share the full command and error string? That will help us pinpoint the cause.

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**Author:** ![frangio](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/frangio/32/15251_2.png) [@frangio](https://forum.openzeppelin.com/u/frangio)\
**Post date:** [April 1, 2019, 5:58pm UTC](https://forum.openzeppelin.com/t/erc721-contract/459/5 "2019-04-01T17:58:36Z")

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Unfortunately that guide was outdated. Sorry! The error you were getting was due to some changes in the `Counter` library introduced in [OpenZeppelin 2.2](https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/CHANGELOG.md#220-2019-03-14).

I’ve just fixed it. Please take a look at it [here](https://github.com/OpenZeppelin/openzeppelin-docsite/blob/master/docs/docs/learn-about-tokens.md#erc721).

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**Author:** ![mssmx](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/mssmx/32/345_2.png) [@mssmx](https://forum.openzeppelin.com/u/mssmx)\
**Post date:** [April 2, 2019, 4:58am UTC](https://forum.openzeppelin.com/t/erc721-contract/459/6 "2019-04-02T04:58:23Z")

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Thank you very much! You are a great team!