# UDT Instance: Syntax Error on Token 'IDENTIFIER'

**URL:** <https://forum.inductiveautomation.com/t/udt-instance-syntax-error-on-token-identifier/11391>\
**Category:** Ignition\
**Created:** [March 21, 2016, 12:33pm UTC](https://forum.inductiveautomation.com/t/udt-instance-syntax-error-on-token-identifier/11391 "2016-03-21T12:33:59Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![cmisztur2](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/cmisztur2/32/4243_2.png) [@cmisztur2](https://forum.inductiveautomation.com/u/cmisztur2)\
**Post date:** [March 21, 2016, 12:33pm UTC](https://forum.inductiveautomation.com/t/udt-instance-syntax-error-on-token-identifier/11391/1 "2016-03-21T12:33:59Z")

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I am experiencing strange behavior in 7.8 where a UDT instance created using system.tag.addTag does not allow an string Expression Tag to contain letters, only numbers.

Here is how I create the instance:

Here is the expression tag:

Here are the instance parameters:

Everything is good so far.

Now I add the letter ‘f’ to ClientId parameter:

And here is the instance error:

/c

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<div class="post-metadata">

**Author:** ![cmisztur2](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/cmisztur2/32/4243_2.png) [@cmisztur2](https://forum.inductiveautomation.com/u/cmisztur2)\
**Post date:** [March 21, 2016, 12:41pm UTC](https://forum.inductiveautomation.com/t/udt-instance-syntax-error-on-token-identifier/11391/2 "2016-03-21T12:41:22Z")

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Nevermind. ![:scratch:](https://us1.discourse-cdn.com/inductiveautomation/original/1X/76d1620bec252bfac07050c889ff5a91dc8a9c25.gif ":scratch:")