From Jim Meyering

(jm_AC_PREREQ_XSTRTOUMAX): Check for declaration of strtoumax

m4/xstrtoumax.m4

@@ -8,7 +8,7 @@ AC_DEFUN([jm_AC_PREREQ_XSTRTOUMAX],
   AC_REQUIRE([jm_AC_TYPE_UINTMAX_T])
   AC_REQUIRE([jm_AC_TYPE_LONG_LONG])
   AC_REQUIRE([jm_AC_TYPE_UNSIGNED_LONG_LONG])
-  AC_CHECK_DECLS([strtoul, strtoull])
+  AC_CHECK_DECLS([strtoul, strtoull, strtoumax])
   AC_CHECK_HEADERS(limits.h stdlib.h inttypes.h)
 
   AC_CACHE_CHECK([whether <inttypes.h> defines strtoumax as a macro],