diff --git a/lib/jsdoc/util/templateHelper.js b/lib/jsdoc/util/templateHelper.js
index 28843ef8..035e85ad 100644
--- a/lib/jsdoc/util/templateHelper.js
+++ b/lib/jsdoc/util/templateHelper.js
@@ -45,7 +45,7 @@ function makeUniqueFilename(filename, str) {
 
     // don't allow filenames to begin with an underscore
     if (!filename.length || filename[0] === '_') {
-        filename = 'X' + filename;
+        filename = '-' + filename;
         key = filename.toLowerCase();
     }
 
diff --git a/test/specs/jsdoc/util/templateHelper.js b/test/specs/jsdoc/util/templateHelper.js
index e068465d..940bb5eb 100644
--- a/test/specs/jsdoc/util/templateHelper.js
+++ b/test/specs/jsdoc/util/templateHelper.js
@@ -212,7 +212,7 @@ describe("jsdoc/util/templateHelper", function() {
         });
 
         it('should not allow a filename to start with an underscore', function() {
-            expect( helper.getUniqueFilename('') ).toBe('X_.html');
+            expect( helper.getUniqueFilename('') ).toBe('-_.html');
         });
 
         it('should not return the same filename twice', function() {