diff --git a/packages/behavior/context.js b/packages/behavior/context.js
index 70ff9af..e3efba2 100644
--- a/packages/behavior/context.js
+++ b/packages/behavior/context.js
@@ -19,7 +19,9 @@ export default class Context {
   }
 
   add(key, value, type = 'undefined') {
-    this.map.set(key, [value, type]);
+    if (key) {
+      this.map.set(key, [value, type]);
+    }
   }
 
   addObjectMap(map) {