diff --git a/tools/safe-pathwatcher.js b/tools/safe-pathwatcher.js
index f57d68f71c..fbda8c4049 100644
--- a/tools/safe-pathwatcher.js
+++ b/tools/safe-pathwatcher.js
@@ -64,7 +64,10 @@ exports.testDirectory = function (dir) {
 
   try {
     // Watch the candidate directory using pathwatcher.watch.
-    var watcher = files.pathwatcherWatch(dir, cleanUp);
+    var watcher = files.pathwatcherWatch(dir, function () {
+      cleanUp();
+      switchFunctions = null;
+    });
 
   } catch (err) {
     // If the directory did not exist, do not treat this failure as
@@ -110,17 +113,19 @@ exports.watch = function (absPath, callback) {
     var closed = false;
     var switched = false;
 
-    switchFunctions.push(function switchToPolling() {
-      if (! switched && ! closed) {
-        switched = true;
-        watcher.close();
+    if (switchFunctions) {
+      switchFunctions.push(function switchToPolling() {
+        if (! switched && ! closed) {
+          switched = true;
+          watcher.close();
 
-        // Re-watch the file using files.watchFile instead.
-        files.watchFile(absPath, {
-          interval: pollingInterval
-        }, callback);
-      }
-    });
+          // Re-watch the file using files.watchFile instead.
+          files.watchFile(absPath, {
+            interval: pollingInterval
+          }, callback);
+        }
+      });
+    }
 
     return {
       close: function close() {