-char *with_thousand_seps (wgint);
-#ifndef with_thousand_seps_sum
-char *with_thousand_seps_sum (SUM_SIZE_INT);
+const char *with_thousand_seps (wgint);
+
+/* human_readable must be able to accept wgint and SUM_SIZE_INT
+ arguments. On machines where wgint is 32-bit, declare it to accept
+ double. */
+#if SIZEOF_WGINT >= 8
+# define HR_NUMTYPE wgint
+#else
+# define HR_NUMTYPE double