Latest 2.1 breaks during compilation

[hickscorp]

2.1 published yesterday doesn't compile for us:

===> Compiling keccakf1600
make: Entering directory 'a/deps/keccakf1600/c_src'
 C      decaf-utils.c
 C      keccakf1600_nif.c
In file included from a/deps/keccakf1600/c_src/keccakf1600_nif.c:4:
a/deps/keccakf1600/c_src/keccakf1600_nif.h:9:10: fatal error: erl_nif.h: No such file or directory
    9 | #include <erl_nif.h>
      |          ^~~~~~~~~~~
compilation terminated.
make: *** [Makefile:151: a/deps/keccakf1600/c_src/keccakf1600_nif.o] Error 1
make: Leaving directory 'a/deps/keccakf1600/c_src'
===> Hook for compile failed!

We're using erlang 22.3.