diff --git a/src/wrap.c b/src/wrap.c
index 66f1e22..a082a18 100644
--- a/src/wrap.c
+++ b/src/wrap.c
@@ -66,6 +66,10 @@ static enum ec3_status add_file(
 
 	while (1) {
 		size_t r = fread(buf, 1, cluster_size, inp);
+		if (r == 0) {
+			break;
+		}
+
 		size_t w;
 		status = ec3_tag_ioctx_write_cluster(tag, i++, buf, r, &w);