protonscr

DIablo IV - Wine missing implementation of "FindNextFileNameW"

protonclosed
ValveSoftware/Proton#9931 · opened 2026-07-01 by DrSuperGood · updated 2026-07-02 · 2 comments · github
DDrSuperGood 2026-07-01 github

Compatibility Report

  • Name of the game with compatibility issues: Diablo IV
  • Steam AppID of the game: 2344520

System Information

  • Steam Deck (not mine)

I confirm:

  • [yes] that I haven't found an existing compatibility report for this game.
  • [N/A] that I have checked whether there are updates for my system available.

Symptoms

People are reporting that starting Diablo IV on their steam deck is now throwing that the FindNextFileNameW function is missing. This has likely been brought on by Blizzard updating the game and starting to use this API function.

Looking through Wine in the current and bleeding edge branch, this function is stubbed and so does not appear implemented. This is a Windows fileapi.h function that does not appear deprecated so it seems reasonable to expect some game devs to use it.

There is a fair chance that Blizzard will try to patch this issue from their end by working around using that function. Still I would suggest that some implementation of FindNextFileNameW is made, even if very slow, so that future game devs who decide to use this function do not accidently run into proton compatibility problems.

Reproduction

Apparently trying to start Diablo IV on a steam deck as of 7:00 AM UK time on the 1st of July 2026.

Ffluffynuts 2026-07-01 github

I haven't seen an error specific to this report, but I can report that since last night (30.06.2026), Diablo4 no longer launches with any variant of proton that I try (experimental, 11, GE versions, cachyos-ge version).
The launcher still starts up, but when I click "Play", the button text changes to "Launching", then after a bit "Playing", then instantly back to "Play". No window shown, nothing in logs that I (or claude - i threw a lot of logs there) could find except an error from diablo_iv_loader.dll (which may be the above error, but it wasn't surfaced with that name, iirc)

Kkisak-valve maintainer 2026-07-01 github

Hello @DrSuperGood, we're using one issue report per unofficially supported game title. Closing as a duplicate of #7199.

As a side note, reporting a game is using an API call second hand without evidence isn't particularly useful.

DLLs