# Error: unrecognized iuse function MUTAGEN

**URL:** <https://discourse.cataclysmdda.org/t/error-unrecognized-iuse-function-mutagen/16064>\
**Category:** The Garage\
**Created:** [August 2, 2018, 8:58am UTC](https://discourse.cataclysmdda.org/t/error-unrecognized-iuse-function-mutagen/16064 "2018-08-02T08:58:07Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![DaWhatTheFox](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/dawhatthefox/32/1307_2.png) [@DaWhatTheFox](https://discourse.cataclysmdda.org/u/DaWhatTheFox)\
**Post date:** [August 2, 2018, 8:58am UTC](https://discourse.cataclysmdda.org/t/error-unrecognized-iuse-function-mutagen/16064/1 "2018-08-02T08:58:08Z")

</div>

This is kind of a continuation from my other thread about “threshold\_mut”… sort of.  
So now I am getting the following error on the Arcana mod:  
 ![](https://us1.discourse-cdn.com/flex016/uploads/cataclysmdda/original/2X/b/bb686c3eff3d331164821eb898d807ffc3fd1f29.png)  
Which I believe I have pinpointed to the “use\_action” function for tools.json  
 ![](https://us1.discourse-cdn.com/flex016/uploads/cataclysmdda/original/2X/c/cd186f91ce623f7ec039d09e1df090658febc5a7.png)  
But now the question is, why is this giving an error now? And how would I be able to fix it myself?

---

<div class="post-metadata">

**Author:** ![Zhilkin](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/zhilkin/32/3749_2.png) [@Zhilkin](https://discourse.cataclysmdda.org/u/Zhilkin)\
**Post date:** [August 2, 2018, 3:33pm UTC](https://discourse.cataclysmdda.org/t/error-unrecognized-iuse-function-mutagen/16064/2 "2018-08-02T15:33:28Z")

</div>

iuse action was renamed from `MUTAGEN` to `mutagen` (in lowercase), so you need to changed that - probably some more changes will be required to make everything to work properly.

See all changes in [https://github.com/CleverRaven/Cataclysm-DDA/pull/24183/files](https://github.com/CleverRaven/Cataclysm-DDA/pull/24183/files).

---

<div class="post-metadata">

**Author:** ![DaWhatTheFox](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/dawhatthefox/32/1307_2.png) [@DaWhatTheFox](https://discourse.cataclysmdda.org/u/DaWhatTheFox)\
**Post date:** [August 2, 2018, 4:10pm UTC](https://discourse.cataclysmdda.org/t/error-unrecognized-iuse-function-mutagen/16064/3 "2018-08-02T16:10:10Z")

</div>

Update: I replaced MUTAGEN, in all caps, to mutagen, in all lowers, and that did the trick. Nonetheless I found an error with “MUT\_IV” later, but replacing that with “mutagen\_iv” was good enough.

Nocts’ Cataclysm++ mod too showed the “MUT\_IV” error in tools.json, as well as the mod “Mutation changes” in the file mutations.json (this one also had MUTAGEN in all caps in the same file).