diff --git a/lib/child_process.js b/lib/child_process.js
index 4812086606..bb80ac11d9 100644
--- a/lib/child_process.js
+++ b/lib/child_process.js
@@ -369,6 +369,7 @@ function ChildProcess() {
 
   this.signalCode = null;
   this.exitCode = null;
+  this.killed = false;
 
   this._internal = new Process();
   this._internal.onexit = function(exitCode, signalCode) {