diff --git a/lib/board.js b/lib/board.js
index a1acf89..1da3074 100644
--- a/lib/board.js
+++ b/lib/board.js
@@ -42,10 +42,10 @@ var Board = function (options) {
           process.on('SIGINT', function(){
             self.log('info', 'sending debug mode toggle off to board');
             self.write('99' + self.normalizePin(0) + self.normalizeVal(0));
-            delete self.serial;
-            setTimeout(function(){
-              process.exit();
-            }, 100);
+            self.serial.once('close', function() {
+              setTimeout(process.exit, 100);
+            });
+            self.serial.close();
           });
         }