Compilation error

dll.c: In function 'load':
<command-line>: error: 'UNKNOWN' undeclared (first use in this function); did you mean 'DT_UNKNOWN'?
dll.c:503:18: note: in expansion of macro 'V_MAJOR'
  503 |   dir, be->name, V_MAJOR);
      |                  ^~~~~~~
<command-line>: note: each undeclared identifier is reported only once for each function it appears in
dll.c:503:18: note: in expansion of macro 'V_MAJOR'
  503 |   dir, be->name, V_MAJOR);
      |                  ^~~~~~~
In file included from dll.c:133:
dll.c: In function 'sane_dll_init':
./../include/sane/config.h:513:26: error: 'UNKNOWN' undeclared (first use in this function); did you mean 'DT_UNKNOWN'?
  513 | #define SANE_DLL_V_MAJOR UNKNOWN
      |                          ^~~~~~~
../include/sane/sane.h:31:21: note: in definition of macro 'SANE_VERSION_CODE'
   31 |   (  (((SANE_Word) (major) &   0xff) << 24) \
      |                     ^~~~~
dll.c:926:40: note: in expansion of macro 'SANE_DLL_V_MAJOR'
  926 |     *version_code = SANE_VERSION_CODE (SANE_DLL_V_MAJOR, SANE_DLL_V_MINOR,
      |                                        ^~~~~~~~~~~~~~~~
../include/sane/sane.h:32:26: error: expected expression before ')' token
   32 |    | (((SANE_Word) (minor) &   0xff) << 16) \
      |                          ^
dll.c:926:21: note: in expansion of macro 'SANE_VERSION_CODE'
  926 |     *version_code = SANE_VERSION_CODE (SANE_DLL_V_MAJOR, SANE_DLL_V_MINOR,
      |                     ^~~~~~~~~~~~~~~~~
../include/sane/sane.h:33:26: error: expected expression before ')' token
   33 |    | (((SANE_Word) (build) & 0xffff) <<  0))
      |                          ^
dll.c:926:21: note: in expansion of macro 'SANE_VERSION_CODE'
  926 |     *version_code = SANE_VERSION_CODE (SANE_DLL_V_MAJOR, SANE_DLL_V_MINOR,
      |                     ^~~~~~~~~~~~~~~~~
make[3]: *** [Makefile:4630: libdll_preload_la-dll.lo] Error 1
make[3]: Leaving directory '/build/backends-1.0.32/backend'
make[2]: *** [Makefile:3338: all] Error 2
make[2]: Leaving directory '/build/backends-1.0.32/backend'
make[1]: *** [Makefile:607: all-recursive] Error 1
make[1]: Leaving directory '/build/backends-1.0.32'
make: *** [Makefile:497: all] Error 2

Compiling on NixOS 20.09, linux x86_64, from a checkout of 1.0.32.