diff --git a/README.md b/README.md
index bdffb425..85a36acd 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# BrowserFS v1.4.1
+# BrowserFS v1.4.2
 > BrowserFS is an in-browser file system that emulates the [Node JS file system API](http://nodejs.org/api/fs.html) and supports storing and retrieving files from various backends. BrowserFS also integrates nicely into the Emscripten file system.
 
 [![Build Status](https://travis-ci.org/jvilk/BrowserFS.svg?branch=master)](https://travis-ci.org/jvilk/BrowserFS)
diff --git a/package.json b/package.json
index 352533ac..19676fe4 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "browserfs",
-  "version": "1.4.1",
+  "version": "1.4.2",
   "description": "A filesystem in your browser!",
   "main": "dist/browserfs.js",
   "typings": "dist/browserfs",
diff --git a/src/core/browserfs.ts b/src/core/browserfs.ts
index 5a4641d1..3ee5d4c1 100644
--- a/src/core/browserfs.ts
+++ b/src/core/browserfs.ts
@@ -142,13 +142,15 @@ export function getFileSystem(config: FileSystemConfiguration, cb: BFSCallback<F
       }
     }
   }
+
   if (options !== null && typeof(options) === "object") {
+    let finishedIterating = false;
     const props = Object.keys(options).filter((k) => k !== 'fs');
 
     // Check recursively if other fields have 'fs' properties.
     props.forEach((p) => {
       const d = options[p];
-      if (d['fs']) {
+      if (d !== null && typeof(d) === "object" && d['fs']) {
         waitCount++;
         getFileSystem(d, function(e, fs?) {
           waitCount--;
@@ -160,13 +162,14 @@ export function getFileSystem(config: FileSystemConfiguration, cb: BFSCallback<F
             cb(e);
           } else {
             options[p] = fs;
-            if (waitCount === 0) {
+            if (waitCount === 0 && finishedIterating) {
               finish();
             }
           }
         });
       }
     });
+    finishedIterating = true;
   }
   if (waitCount === 0) {
     finish();