diff --git a/src/dispatchers/dispatcher.ts b/src/dispatchers/dispatcher.ts
index bd8909d7a7..aeee3d7708 100644
--- a/src/dispatchers/dispatcher.ts
+++ b/src/dispatchers/dispatcher.ts
@@ -91,6 +91,7 @@ export class Dispatcher<Type, Initializer> extends EventEmitter implements chann
 
   _dispose() {
     assert(!this._disposed);
+    this._disposed = true;
 
     // Clean up from parent and connection.
     if (this._parent)