diff --git a/lib/constants.js b/lib/constants.js
index 7682f39..3dcc50c 100644
--- a/lib/constants.js
+++ b/lib/constants.js
@@ -503,7 +503,8 @@ const keyFlags = {
   SEP: 1 << 0,
   // 1-6 reserved
   REVOKE: 1 << 7,
-  ZONE: 1 << 8
+  ZONE: 1 << 8,
+  ZSK: 1 << 8,
   // 9-15 reserved
 };