diff --git a/m4/xstrtoumax.m4 b/m4/xstrtoumax.m4
index 7ea69a92edd2e01dde4f89fba325bedc85440377..d1ece9b5df4ed41722c60070958ae078929f9faa 100644
--- a/m4/xstrtoumax.m4
+++ b/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],