Missing MD4 Kernel Module

My mount.cifs is complaining about lack of MD4 (and it doesn’t mount anymore - smbclient does work however).

[60493.402837] CIFS: VFS: Could not allocate crypto md4

Any hints how I can install it again? I can mount from other machines, and they have MD4 module installed:

> lsmod | grep md4
md4                    16384  0

Adding this seems to work:

boot.kernelModules = [ "md4" ];

unsure how it happened - lack of rebooting might have hidden the problem for a long time before I noticed…