--- a/toolkit/components/osfile/osfile_unix_allthreads.jsm
+++ b/toolkit/components/osfile/osfile_unix_allthreads.jsm
@@ -309,9 +309,13 @@ if (typeof Components != "undefined") {
   // Special constructors that need to be defined on all threads
   OSError.closed = function closed(operation) {
     return new OSError(operation, OS.Constants.libc.EBADF);
   };
 
   OSError.exists = function exists(operation) {
     return new OSError(operation, OS.Constants.libc.EEXIST);
   };
+
+  OSError.noSuchFile = function noSuchFile(operation) {
+    return new OSError(operation, OS.Constants.libc.ENOENT);
+  };
 })(this);

--- a/toolkit/components/osfile/osfile_unix_front.jsm
+++ b/toolkit/components/osfile/osfile_unix_front.jsm
@@ -602,34 +602,47 @@
       * @param {*=} options Ignored in this implementation.
       *
       * @throws {File.Error} If |path| does not represent a directory or
       * if the directory cannot be iterated.
       * @constructor
       */
      File.DirectoryIterator = function DirectoryIterator(path, options) {
        exports.OS.Shared.AbstractFile.AbstractIterator.call(this);
-       let dir = throw_on_null("DirectoryIterator", UnixFile.opendir(path));
-       this._dir = dir;
        this._path = path;
+       this._dir = UnixFile.opendir(this._path);
+       if (this._dir == null) {
+         let error = ctypes.errno;
+         if (error != OS.Constants.libc.ENOENT) {
+           throw new File.Error("DirectoryIterator", error);
+         }
+         this._exists = false;
+         this._closed = true;
+       } else {
+         this._exists = true;
+         this._closed = false;
+       }
      };
      File.DirectoryIterator.prototype = Object.create(exports.OS.Shared.AbstractFile.AbstractIterator.prototype);
 
      /**
       * Return the next entry in the directory, if any such entry is
       * available.
       *
       * Skip special directories "." and "..".
       *
       * @return {File.Entry} The next entry in the directory.
       * @throws {StopIteration} Once all files in the directory have been
       * encountered.
       */
      File.DirectoryIterator.prototype.next = function next() {
-       if (!this._dir) {
+       if (!this._exists) {
+         throw File.Error.noSuchFile("DirectoryIterator.prototype.next");
+       }
+       if (this._closed) {
          throw StopIteration;
        }
        for (let entry = UnixFile.readdir(this._dir);
             entry != null && !entry.isNull();
             entry = UnixFile.readdir(this._dir)) {
          let contents = entry.contents;
          if (contents.d_type == OS.Constants.libc.DT_DIR) {
            let name = contents.d_name.readString();
@@ -643,21 +656,31 @@
        throw StopIteration;
      };
 
      /**
       * Close the iterator and recover all resources.
       * You should call this once you have finished iterating on a directory.
       */
      File.DirectoryIterator.prototype.close = function close() {
-       if (!this._dir) return;
+       if (this._closed) return;
+       this._closed = true;
        UnixFile.closedir(this._dir);
        this._dir = null;
      };
 
+    /**
+     * Determine whether the directory exists.
+     *
+     * @return {boolean}
+     */
+     File.DirectoryIterator.prototype.exists = function exists() {
+       return this._exists;
+     };
+
      /**
       * Return directory as |File|
       */
      File.DirectoryIterator.prototype.unixAsFile = function unixAsFile() {
        if (!this._dir) throw File.Error.closed();
        return error_or_file(UnixFile.dirfd(this._dir));
      };