diff --git a/lib/jsdoc/util/templateHelper.js b/lib/jsdoc/util/templateHelper.js
index 876e6a68..2c230527 100644
--- a/lib/jsdoc/util/templateHelper.js
+++ b/lib/jsdoc/util/templateHelper.js
@@ -42,6 +42,12 @@ function makeUniqueFilename(filename, str) {
     var key = filename.toLowerCase();
     var nonUnique = true;
 
+    // don't allow filenames to begin with an underscore
+    if (!filename.length || filename[0] === '_') {
+      filename = 'X' + filename;
+      key = filename.toLowerCase();
+    }
+
     // append enough underscores to make the filename unique
     while (nonUnique) {
         if ( hasOwnProp.call(files, key) ) {
diff --git a/test/specs/jsdoc/util/templateHelper.js b/test/specs/jsdoc/util/templateHelper.js
index a01cefa2..c4586b10 100644
--- a/test/specs/jsdoc/util/templateHelper.js
+++ b/test/specs/jsdoc/util/templateHelper.js
@@ -1,16 +1,16 @@
-/*global afterEach, beforeEach, describe, expect, env, it, jasmine, spyOn, xdescribe */
 /*eslint quotes:0 */
 'use strict';
 
 var hasOwnProp = Object.prototype.hasOwnProperty;
 
 describe("jsdoc/util/templateHelper", function() {
-    var helper = require('jsdoc/util/templateHelper'),
-        doclet = require('jsdoc/doclet'),
-        doop = require('jsdoc/util/doop'),
-        logger = require('jsdoc/util/logger'),
-        resolver = require('jsdoc/tutorial/resolver'),
-        taffy = require('taffydb').taffy;
+    var helper = require('jsdoc/util/templateHelper');
+    var doclet = require('jsdoc/doclet');
+    var doop = require('jsdoc/util/doop');
+    var logger = require('jsdoc/util/logger');
+    var resolver = require('jsdoc/tutorial/resolver');
+    var taffy = require('taffydb').taffy;
+
     helper.registerLink('test', 'path/to/test.html');
 
     it("should exist", function() {
@@ -202,6 +202,10 @@ describe("jsdoc/util/templateHelper", function() {
             expect(filename).toBe('a very strange __________ filename.html');
         });
 
+        it('should not allow a filename to start with an underscore', function() {
+            expect( helper.getUniqueFilename('') ).toBe('X_.html');
+        });
+
         it('should not return the same filename twice', function() {
             var name = 'polymorphic';
             var filename1 = helper.getUniqueFilename(name);