Problem with zfs.ko: lockstat_enabled symbol

I recently updated my other laptop, and now I'm getting a problem
loading zfs.ko at boot, relating to the lockstat_enabled symbol not
being defined (this happens during kernel boot and prevents mounting
root, so I can't get an exact trace)

Looking at the new kernel, it seems that only zfs.ko contains the symbol
lockstat_enabled (notably, kernel does not).  In my old kernel, zfs.ko
does not contain a reference to that symbol.

Has anyone else seen this?  Is there a workaround, or was this a one-off
bug?