diff --git a/libutil/human.c b/libutil/human.c
index eb5d0b7..91679bc 100644
--- a/libutil/human.c
+++ b/libutil/human.c
@@ -1,11 +1,12 @@
 /* See LICENSE file for copyright and license details. */
 #include <stdio.h>
 #include <string.h>
+#include <stdint.h>
 
 #include "../util.h"
 
 char *
-humansize(size_t n)
+humansize(uintmax_t n)
 {
 	static char buf[16];
 	const char postfixes[] = "BKMGTPE";
@@ -16,7 +17,7 @@ humansize(size_t n)
 		size /= 1024;
 
 	if (!i)
-		snprintf(buf, sizeof(buf), "%zu", n);
+		snprintf(buf, sizeof(buf), "%ju", n);
 	else
 		snprintf(buf, sizeof(buf), "%.1f%c", size, postfixes[i]);
 
diff --git a/util.h b/util.h
index bd8ddc0..4784fa2 100644
--- a/util.h
+++ b/util.h
@@ -66,7 +66,7 @@ int eregcomp(regex_t *, const char *, int);
 void enmasse(int, char **, int (*)(const char *, const char *, int));
 void fnck(const char *, const char *, int (*)(const char *, const char *, int), int);
 mode_t getumask(void);
-char *humansize(size_t);
+char *humansize(uintmax_t);
 mode_t parsemode(const char *, mode_t, mode_t);
 void putword(FILE *, const char *);
 #undef strtonum