diff --git a/tests/knot/test_journal.c b/tests/knot/test_journal.c
index 748ab02d02622269801a1596fd51e87c2621a612..750fad871772cee305b908c231bf20df4b66ed51 100644
--- a/tests/knot/test_journal.c
+++ b/tests/knot/test_journal.c
@@ -557,7 +557,7 @@ static knot_dname_t *tm_owner(const char *prefix, const knot_dname_t *apex)
 
 static knot_dname_t *tm_owner_int(int x, const knot_dname_t *apex)
 {
-	char buf[12] = { 0 };
+	char buf[13] = { 0 };
 	(void)snprintf(buf, sizeof(buf), "i%d", x);
 	return tm_owner(buf, apex);
 }