diff --git a/toolkit/components/search/tests/xpcshell/test_addEngine_callback.js b/toolkit/components/search/tests/xpcshell/test_addEngine_callback.js
index 88f6b1e395b5..22daf16d5f88 100644
--- a/toolkit/components/search/tests/xpcshell/test_addEngine_callback.js
+++ b/toolkit/components/search/tests/xpcshell/test_addEngine_callback.js
@@ -8,6 +8,8 @@
 "use strict";
 
 const Ci = Components.interfaces;
+let gHttpServer;
+let gBaseUrl;
 
 Components.utils.import("resource://testing-common/httpd.js");
 
@@ -67,7 +69,7 @@ add_test(function simple_callback_test() {
       do_throw("search callback returned error: " + errorCode);
     }
   }
-  Services.search.addEngine("http://localhost:4444/data/engine.xml",
+  Services.search.addEngine(gBaseUrl + "/data/engine.xml",
                             Ci.nsISearchEngine.DATA_XML,
                             null, false, searchCallback);
 });
@@ -85,7 +87,7 @@ add_test(function duplicate_failure_test() {
     }
   }
   // Re-add the same engine added in the previous test
-  Services.search.addEngine("http://localhost:4444/data/engine.xml",
+  Services.search.addEngine(gBaseUrl + "/data/engine.xml",
                             Ci.nsISearchEngine.DATA_XML,
                             null, false, searchCallback);
 });
@@ -111,12 +113,13 @@ add_test(function load_failure_test() {
 function run_test() {
   updateAppInfo();
 
-  let httpServer = new HttpServer();
-  httpServer.start(4444);
-  httpServer.registerDirectory("/", do_get_cwd());
+  gHttpServer = new HttpServer();
+  gHttpServer.start(-1);
+  gHttpServer.registerDirectory("/", do_get_cwd());
+  gBaseUrl = "http://localhost:" + gHttpServer.identity.primaryPort;
 
   do_register_cleanup(function cleanup() {
-    httpServer.stop(function() {});
+    gHttpServer.stop(function() {});
   });
 
   run_next_test();
diff --git a/toolkit/components/search/tests/xpcshell/test_defaultEngine.js b/toolkit/components/search/tests/xpcshell/test_defaultEngine.js
index 7c35e8fcb662..cb8cf7e84aa0 100644
--- a/toolkit/components/search/tests/xpcshell/test_defaultEngine.js
+++ b/toolkit/components/search/tests/xpcshell/test_defaultEngine.js
@@ -77,8 +77,9 @@ function run_test() {
   updateAppInfo();
 
   let httpServer = new HttpServer();
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer.registerDirectory("/", do_get_cwd());
+  let baseUrl = "http://localhost:" + httpServer.identity.primaryPort;
 
   do_register_cleanup(function cleanup() {
     httpServer.stop(function() {});
@@ -89,10 +90,10 @@ function run_test() {
 
   Services.obs.addObserver(search_observer, "browser-search-engine-modified", false);
 
-  Services.search.addEngine("http://localhost:4444/data/engine.xml",
+  Services.search.addEngine(baseUrl + "/data/engine.xml",
                             Ci.nsISearchEngine.DATA_XML,
                             null, false);
-  Services.search.addEngine("http://localhost:4444/data/engine2.xml",
+  Services.search.addEngine(baseUrl + "/data/engine2.xml",
                             Ci.nsISearchEngine.DATA_XML,
                             null, false);
 }
diff --git a/toolkit/components/search/tests/xpcshell/test_nocache.js b/toolkit/components/search/tests/xpcshell/test_nocache.js
index 600a2229d556..0b8ce5c6869f 100644
--- a/toolkit/components/search/tests/xpcshell/test_nocache.js
+++ b/toolkit/components/search/tests/xpcshell/test_nocache.js
@@ -25,7 +25,7 @@ function run_test()
   do_load_manifest("data/chrome.manifest");
 
   let httpServer = new HttpServer();
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer.registerDirectory("/", do_get_cwd());
 
   let search = Services.search;
@@ -93,8 +93,9 @@ function run_test()
     Services.obs.addObserver(observer, "browser-search-engine-modified", false);
 
     // Add an engine, check if it appears in the cache
-    search.addEngine("http://localhost:4444/data/engine.xml",
-                   Ci.nsISearchEngine.DATA_XML,
-                   null, false);
+    search.addEngine("http://localhost:" + httpServer.identity.primaryPort +
+                     "/data/engine.xml",
+                     Ci.nsISearchEngine.DATA_XML,
+                     null, false);
   });
 }
diff --git a/toolkit/components/search/tests/xpcshell/test_nodb_pluschanges.js b/toolkit/components/search/tests/xpcshell/test_nodb_pluschanges.js
index be2cab16474a..9cccdb38acb6 100644
--- a/toolkit/components/search/tests/xpcshell/test_nodb_pluschanges.js
+++ b/toolkit/components/search/tests/xpcshell/test_nodb_pluschanges.js
@@ -35,8 +35,9 @@ function run_test()
   do_load_manifest("data/chrome.manifest");
 
   let httpServer = new HttpServer();
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer.registerDirectory("/", do_get_cwd());
+  let baseUrl = "http://localhost:" + httpServer.identity.primaryPort;
 
   let search = Services.search;
 
@@ -93,12 +94,12 @@ function run_test()
 
   do_test_pending();
 
-  search.addEngine("http://localhost:4444/data/engine.xml",
+  search.addEngine(baseUrl + "/data/engine.xml",
                    Ci.nsISearchEngine.DATA_XML,
                    null, false);
-  search.addEngine("http://localhost:4444/data/engine.src",
+  search.addEngine(baseUrl + "/data/engine.src",
                    Ci.nsISearchEngine.DATA_TEXT,
-                   "http://localhost:4444/data/ico-size-16x16-png.ico",
+                   baseUrl + "/data/ico-size-16x16-png.ico",
                    false);
 
   do_timeout(120000, function() {
diff --git a/toolkit/components/search/tests/xpcshell/test_notifications.js b/toolkit/components/search/tests/xpcshell/test_notifications.js
index 485ed0e6e136..e5c18b4b67ad 100644
--- a/toolkit/components/search/tests/xpcshell/test_notifications.js
+++ b/toolkit/components/search/tests/xpcshell/test_notifications.js
@@ -64,7 +64,7 @@ function run_test() {
   updateAppInfo();
 
   let httpServer = new HttpServer();
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer.registerDirectory("/", do_get_cwd());
 
   do_register_cleanup(function cleanup() {
@@ -76,7 +76,9 @@ function run_test() {
 
   Services.obs.addObserver(search_observer, "browser-search-engine-modified", false);
 
-  Services.search.addEngine("http://localhost:4444/data/engine.xml",
+  Services.search.addEngine("http://localhost:" +
+                            httpServer.identity.primaryPort +
+                            "/data/engine.xml",
                             Ci.nsISearchEngine.DATA_XML,
                             null, false);
 }
diff --git a/toolkit/components/search/tests/xpcshell/test_prefSync.js b/toolkit/components/search/tests/xpcshell/test_prefSync.js
index 29b386ca6af7..29b4f5001d85 100644
--- a/toolkit/components/search/tests/xpcshell/test_prefSync.js
+++ b/toolkit/components/search/tests/xpcshell/test_prefSync.js
@@ -108,8 +108,9 @@ function run_test() {
   updateAppInfo();
 
   let httpServer = new HttpServer();
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer.registerDirectory("/", do_get_cwd());
+  let baseUrl = "http://localhost:" + httpServer.identity.primaryPort;
 
   do_register_cleanup(function cleanup() {
     httpServer.stop(function() {});
@@ -120,10 +121,10 @@ function run_test() {
 
   Services.obs.addObserver(search_observer, "browser-search-engine-modified", false);
 
-  Services.search.addEngine("http://localhost:4444/data/engine.xml",
+  Services.search.addEngine(baseUrl + "/data/engine.xml",
                    Ci.nsISearchEngine.DATA_XML,
                    null, false);
-  Services.search.addEngine("http://localhost:4444/data/engine2.xml",
+  Services.search.addEngine(baseUrl + "/data/engine2.xml",
                    Ci.nsISearchEngine.DATA_XML,
                    null, false);
 }
diff --git a/toolkit/components/search/tests/xpcshell/test_purpose.js b/toolkit/components/search/tests/xpcshell/test_purpose.js
index 7ff80d8ff28e..256ca21dae66 100644
--- a/toolkit/components/search/tests/xpcshell/test_purpose.js
+++ b/toolkit/components/search/tests/xpcshell/test_purpose.js
@@ -55,7 +55,7 @@ function run_test() {
   do_load_manifest("data/chrome.manifest");
 
   let httpServer = new HttpServer();
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer.registerDirectory("/", do_get_cwd());
 
   do_register_cleanup(function cleanup() {
@@ -66,7 +66,9 @@ function run_test() {
   do_test_pending();
   Services.obs.addObserver(search_observer, "browser-search-engine-modified", false);
 
-  Services.search.addEngine("http://localhost:4444/data/engine.xml",
+  Services.search.addEngine("http://localhost:" +
+                            httpServer.identity.primaryPort +
+                            "/data/engine.xml",
                             Ci.nsISearchEngine.DATA_XML,
                             null, false);
 }
diff --git a/toolkit/components/search/tests/xpcshell/test_save_sorted_engines.js b/toolkit/components/search/tests/xpcshell/test_save_sorted_engines.js
index 95dce1c07161..cd2ee8e8a261 100644
--- a/toolkit/components/search/tests/xpcshell/test_save_sorted_engines.js
+++ b/toolkit/components/search/tests/xpcshell/test_save_sorted_engines.js
@@ -30,8 +30,9 @@ function run_test() {
   updateAppInfo();
 
   let httpServer = new HttpServer();
-  httpServer.start(4444);
+  httpServer.start(-1);
   httpServer.registerDirectory("/", do_get_cwd());
+  let baseUrl = "http://localhost:" + httpServer.identity.primaryPort;
 
   function getSearchMetadata() {
     // Check that search-metadata.json has been created
@@ -109,12 +110,12 @@ function run_test() {
 
   do_test_pending();
 
-  search.addEngine("http://localhost:4444/data/engine.xml",
+  search.addEngine(baseUrl + "/data/engine.xml",
                    Ci.nsISearchEngine.DATA_XML,
                    null, false);
-  search.addEngine("http://localhost:4444/data/engine.src",
+  search.addEngine(baseUrl + "/data/engine.src",
                    Ci.nsISearchEngine.DATA_TEXT,
-                   "http://localhost:4444/data/ico-size-16x16-png.ico",
+                   baseUrl + "/data/ico-size-16x16-png.ico",
                    false);
 
   do_timeout(120000, function() {