# Jbuilder fails to build

**URL:** <https://discuss.ocaml.org/t/jbuilder-fails-to-build/802>\
**Category:** Ecosystem\
**Tags:** jbuilder\
**Created:** [September 3, 2017, 9:59am UTC](https://discuss.ocaml.org/t/jbuilder-fails-to-build/802 "2017-09-03T09:59:13Z")\
**Posts on this page:** 1\
**Showing post:** 18

<div class="post-metadata">

**Author:** ![avsm](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/avsm/32/6_2.png) [@avsm](https://discuss.ocaml.org/u/avsm)\
**Post date:** [October 9, 2017, 2:24pm UTC](https://discuss.ocaml.org/t/jbuilder-fails-to-build/802/18 "2017-10-09T14:24:47Z")

</div>

This has been confirmed to be a problem with an OPAM binary compiled with OCaml 4.05.0, due to changed semantics in the `execvpe` call.

_Workaround:_ Run

```
 eval `opam config env`

```

in your shell before executing the `opam` command.

There is also a proposed PR in OCaml to regain the old `execvpe` behaviour in future releases, and @altgr is investigating backporting a fix into the opam 1.2 branch.

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_[View the full topic](https://discuss.ocaml.org/t/jbuilder-fails-to-build/802)._