diff --git a/lib/marked.js b/lib/marked.js
index e34ac17151..6f7ce06720 100644
--- a/lib/marked.js
+++ b/lib/marked.js
@@ -1289,29 +1289,31 @@ Parser.prototype.tok = function() {
  * Slugger generates header id
  */
 
-function Slugger () {	
-  this.seen = {};	
-}	
+function Slugger () {
+  this.seen = {};
+}
 
 /**
  * Convert string to unique id
  */
 
-Slugger.prototype.slug = function (value) {	
-  var slug = value	
+Slugger.prototype.slug = function (value) {
+  var slug = value
     .toLowerCase()
     .trim()
     .replace(/[\u2000-\u206F\u2E00-\u2E7F\\'!"#$%&()*+,./:;<=>?@[\]^`{|}~]/g, '')
     .replace(/\s/g, '-');
-  
-  var count = this.seen.hasOwnProperty(slug) ? this.seen[slug] + 1 : 0;
-  this.seen[slug] = count;
 
-  if (count > 0) {	
-    slug = slug + '-' + count;	
+  if (this.seen.hasOwnProperty(slug)) {
+    var originalSlug = slug;
+    do {
+      this.seen[originalSlug]++;
+      slug = originalSlug + '-' + this.seen[originalSlug];
+    } while (this.seen.hasOwnProperty(slug));
   }
-  
-  return slug;	
+  this.seen[slug] = 0;
+
+  return slug;
 };
 
 /**
@@ -1648,6 +1650,8 @@ marked.lexer = Lexer.lex;
 marked.InlineLexer = InlineLexer;
 marked.inlineLexer = InlineLexer.output;
 
+marked.Slugger = Slugger;
+
 marked.parse = marked;
 
 if (typeof module !== 'undefined' && typeof exports === 'object') {
diff --git a/test/unit/marked-spec.js b/test/unit/marked-spec.js
index d476ceb57e..4f71a5ae06 100644
--- a/test/unit/marked-spec.js
+++ b/test/unit/marked-spec.js
@@ -2,29 +2,54 @@ var marked = require('../../lib/marked.js');
 
 describe('Test heading ID functionality', function() {
   it('should add id attribute by default', function() {
-    var html = marked('# test');
-    expect(html).toBe('<h1 id="test">test</h1>\n');
+    var renderer = new marked.Renderer();
+    var slugger = new marked.Slugger();
+    var header = renderer.heading('test', 1, 'test', slugger);
+    expect(header).toBe('<h1 id="test">test</h1>\n');
   });
 
-  it('should add unique id for repeating heading 1280', function() {
-    var html = marked('# test\n# test\n# test');
-    expect(html).toBe('<h1 id="test">test</h1>\n<h1 id="test-1">test</h1>\n<h1 id="test-2">test</h1>\n');
+  it('should NOT add id attribute when options set false', function() {
+    var renderer = new marked.Renderer({ headerIds: false });
+    var header = renderer.heading('test', 1, 'test');
+    expect(header).toBe('<h1>test</h1>\n');
   });
+});
 
-  it('should add id with non-latin chars', function() {
-    var html = marked('# привет');
-    expect(html).toBe('<h1 id="привет">привет</h1>\n');
+describe('Test slugger functionality', function() {
+  it('should use lowercase slug', function() {
+    var slugger = new marked.Slugger();
+    expect(slugger.slug('Test')).toBe('test');
   });
 
-  it('should add id without ampersands 857', function() {
-    var html = marked('# This & That Section');
-    expect(html).toBe('<h1 id="this--that-section">This &amp; That Section</h1>\n');
+  it('should be unique to avoid collisions 1280', function() {
+    var slugger = new marked.Slugger();
+    expect(slugger.slug('test')).toBe('test');
+    expect(slugger.slug('test')).toBe('test-1');
+    expect(slugger.slug('test')).toBe('test-2');
   });
 
-  it('should NOT add id attribute when options set false', function() {
-    var options = { headerIds: false };
-    var html = marked('# test', options);
-    expect(html).toBe('<h1>test</h1>\n');
+  it('should be unique to avoid collisions 1401', function() {
+    var slugger = new marked.Slugger();
+    expect(slugger.slug('foo')).toBe('foo');
+    expect(slugger.slug('foo')).toBe('foo-1');
+    expect(slugger.slug('foo 1')).toBe('foo-1-1');
+    expect(slugger.slug('foo-1')).toBe('foo-1-2');
+    expect(slugger.slug('foo')).toBe('foo-2');
+  });
+
+  it('should allow non-latin chars', function() {
+    var slugger = new marked.Slugger();
+    expect(slugger.slug('привет')).toBe('привет');
+  });
+
+  it('should remove ampersands 857', function() {
+    var slugger = new marked.Slugger();
+    expect(slugger.slug('This & That Section')).toBe('this--that-section');
+  });
+
+  it('should remove periods', function() {
+    var slugger = new marked.Slugger();
+    expect(slugger.slug('file.txt')).toBe('filetxt');
   });
 });