diff --git a/free.c b/free.c
index 1aaa5ecb..54825ab0 100644
--- a/free.c
+++ b/free.c
@@ -106,7 +106,7 @@ static const char *scale_size(unsigned long size, int flags, struct commandline_
 	if (!(flags & FREE_HUMANREADABLE)) {
 		if (args.exponent == 1) {
 			/* in bytes, which can not be in SI */
-			snprintf(buf, sizeof(buf), "%ld", (long int)(size * 1024));
+			snprintf(buf, sizeof(buf), "%lld", (long long int)(size * 1024));
 			return buf;
 		}
 		if (args.exponent == 2) {