diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index d9fbad5358..62160ca9d4 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -330,12 +330,12 @@ static int expand_atom(struct strbuf *sb, const char *atom, int len,
 		if (data->mark_query)
 			data->info.sizep = &data->size;
 		else
-			strbuf_addf(sb, "%"PRIuMAX , (uintmax_t)data->size);
+			strbuf_add_uint(sb, data->size);
 	} else if (is_atom("objectsize:disk", atom, len)) {
 		if (data->mark_query)
 			data->info.disk_sizep = &data->disk_size;
 		else
-			strbuf_addf(sb, "%"PRIuMAX, (uintmax_t)data->disk_size);
+			strbuf_add_uint(sb, data->disk_size);
 	} else if (is_atom("rest", atom, len)) {
 		if (data->mark_query)
 			data->split_on_whitespace = 1;