diff --git a/lib/asn1/base/node.js b/lib/asn1/base/node.js
index d676d21..0849631 100644
--- a/lib/asn1/base/node.js
+++ b/lib/asn1/base/node.js
@@ -218,6 +218,14 @@ Node.prototype.implicit = function implicit(num) {
   return this;
 };
 
+Node.prototype.cls = function cls(cls) {
+  const state = this._baseState;
+
+  state.cls = cls;
+
+  return this;
+};
+
 Node.prototype.obj = function obj() {
   const state = this._baseState;
   const args = Array.prototype.slice.call(arguments);