MetaMask / MetaMask/metamask-extension
[Bug]: Sending NFT on a Custom Network - error: TypeError: a.toLowerCase is not a function.
@bschorchit is already working on this.
Since Sep 9, 2025.
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Description
**Describe the bug**
Send an NFT to their own Trezor wallet. They complete the entire confirmation process, but then MetaMask throws this error: TypeError: a.toLowerCase is not a function.
User Details:
Version: Extension v13.2.1 on Chrome
From: 0xb579F895d0883Da7E65282dAf43bc068413C39AE
To: Their own Trezor address
NFT: [0xfC87DAbAA3A4c3E133E8C82e0d9b95298D928215](https://explorer.apertum.io/token/0xa1b761890c36e356f49F9DF8D495FcFFa76857ad/instance/39246?tab=metadata)
Network: [Apertum](https://explorer.apertum.io/) (custom network)
**Expected behavior**
It should be possible to transfer NFTs to another account without an error.
**Screenshots/Recordings**
[MetaMask state logs.json](https://github.com/user-attachments/files/22229774/MetaMask.state.logs.json)
[nkbihfbeogaeaoehlefnkodbefgpgknn-1757204286000.log](https://github.com/user-attachments/files/22229773/nkbihfbeogaeaoehlefnkodbefgpgknn-1757204286000.log)
**Steps to reproduce**
Go to the NFT you want to send
Type the account address to send it to
Get the error screen
**Error messages or log output**
```shell
TypeError: a.toLowerCase is not a function.
```
**Detection stage**
In production (default)
**Version**
13.2.1
**Build type**
None
**Browser**
Chrome
**Operating system**
Windows
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Assessment
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