diff --git a/src/util.js b/src/util.js
index 75190f653..ad915b03f 100644
--- a/src/util.js
+++ b/src/util.js
@@ -57,6 +57,8 @@ function assert(cond, msg) {
     error(msg);
 }
 
+// Combines two URLs. The baseUrl shall be absolute URL. If the url is an
+// absolute URL, it will be returned as is.
 function combineUrl(baseUrl, url) {
   if (url.indexOf(':') >= 0)
     return url;
@@ -67,10 +69,13 @@ function combineUrl(baseUrl, url) {
     return baseUrl.substring(0, i) + url;
   } else {
     // relative path
-    var i = baseUrl.lastIndexOf('#');
-    i = baseUrl.lastIndexOf('?', i < 0 ? baseUrl.length : i);
-    i = baseUrl.lastIndexOf('/', i < 0 ? baseUrl.length : i);
-    return baseUrl.substring(0, i + 1) + url;
+    var pathLength = baseUrl.length, i;
+    i = baseUrl.lastIndexOf('#');
+    pathLength = i >= 0 ? i : pathLength;
+    i = baseUrl.lastIndexOf('?', pathLength);
+    pathLength = i >= 0 ? i : pathLength;
+    var prefixLength = baseUrl.lastIndexOf('/', pathLength);
+    return baseUrl.substring(0, prefixLength + 1) + url;
   }
 }
 PDFJS.combineUrl = combineUrl;
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index 5b068fbb9..e1e0a318d 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -6,7 +6,7 @@
 describe('api', function() {
   // TODO run with worker enabled
   PDFJS.disableWorker = true;
-  var basicApiUrl = '../pdfs/basicapi.pdf';
+  var basicApiUrl = combineUrl(window.location.href, '../pdfs/basicapi.pdf');
   function waitsForPromise(promise) {
     waitsFor(function() {
       return promise.isResolved || promise.isRejected;
diff --git a/test/unit/unit_test.html b/test/unit/unit_test.html
index ca0a1aed1..0291f1a0f 100644
--- a/test/unit/unit_test.html
+++ b/test/unit/unit_test.html
@@ -43,6 +43,7 @@
   <script type="text/javascript" src="stream_spec.js"></script>
   <script type="text/javascript" src="api_spec.js"></script>
   <script type="text/javascript" src="metadata_spec.js"></script>
+  <script type="text/javascript" src="util_spec.js"></script>
   <script type="text/javascript">
     'use strict';
 
diff --git a/test/unit/util_spec.js b/test/unit/util_spec.js
new file mode 100644
index 000000000..c5743d6cc
--- /dev/null
+++ b/test/unit/util_spec.js
@@ -0,0 +1,51 @@
+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
+
+'use strict';
+
+describe('util', function() {
+
+  describe('combineUrl', function() {
+    it('absolute url with protocol stays as is', function() {
+      var baseUrl = 'http://server/index.html';
+      var url = 'http://server2/test2.html';
+      var result = combineUrl(baseUrl, url);
+      var expected = 'http://server2/test2.html';
+      expect(result).toEqual(expected);
+    });
+
+    it('absolute url without protocol uses prefix from base', function() {
+      var baseUrl = 'http://server/index.html';
+      var url = '/test2.html';
+      var result = combineUrl(baseUrl, url);
+      var expected = 'http://server/test2.html';
+      expect(result).toEqual(expected);
+    });
+
+    it('combines relative url with base', function() {
+      var baseUrl = 'http://server/index.html';
+      var url = 'test2.html';
+      var result = combineUrl(baseUrl, url);
+      var expected = 'http://server/test2.html';
+      expect(result).toEqual(expected);
+    });
+
+    it('combines relative url (w/hash) with base', function() {
+      var baseUrl = 'http://server/index.html#!/test';
+      var url = 'test2.html';
+      var result = combineUrl(baseUrl, url);
+      var expected = 'http://server/test2.html';
+      expect(result).toEqual(expected);
+    });
+
+    it('combines relative url (w/query) with base', function() {
+      var baseUrl = 'http://server/index.html?search=/test';
+      var url = 'test2.html';
+      var result = combineUrl(baseUrl, url);
+      var expected = 'http://server/test2.html';
+      expect(result).toEqual(expected);
+    });
+  });
+
+});
+