diff --git a/builtin-count-objects.c b/builtin-count-objects.c
index f5b22bb..6263d8a 100644
--- a/builtin-count-objects.c
+++ b/builtin-count-objects.c
@@ -44,7 +44,7 @@
 			if (lstat(path, &st) || !S_ISREG(st.st_mode))
 				bad = 1;
 			else
-				(*loose_size) += st.st_blocks;
+				(*loose_size) += xsize_t(st.st_blocks);
 		}
 		if (bad) {
 			if (verbose) {