diff --git a/browser/components/sessionstore/src/nsSessionStore.js b/browser/components/sessionstore/src/nsSessionStore.js
index b1d84fbf856b..362c7e7832c4 100644
--- a/browser/components/sessionstore/src/nsSessionStore.js
+++ b/browser/components/sessionstore/src/nsSessionStore.js
@@ -2612,7 +2612,16 @@ SessionStoreService.prototype = {
   _toJSONString: function sss_toJSONString(aJSObject) {
     // XXXzeniko drop the following keys used only for internal bookkeeping:
     //           _tabStillLoading, _hosts, _formDataSaved
-    return JSON.stringify(aJSObject);
+    let jsonString = JSON.stringify(aJSObject);
+    
+    if (/[\u2028\u2029]/.test(jsonString)) {
+      // work-around for bug 485563 until we can use JSON.parse
+      // instead of evalInSandbox everywhere
+      jsonString = jsonString.replace(/[\u2028\u2029]/g,
+                                      function($0) "\\u" + $0.charCodeAt(0).toString(16));
+    }
+    
+    return jsonString;
   },
 
   _notifyIfAllWindowsRestored: function sss_notifyIfAllWindowsRestored() {
diff --git a/browser/components/sessionstore/test/browser/Makefile.in b/browser/components/sessionstore/test/browser/Makefile.in
index a733497eb385..d5d242f4678e 100644
--- a/browser/components/sessionstore/test/browser/Makefile.in
+++ b/browser/components/sessionstore/test/browser/Makefile.in
@@ -81,6 +81,7 @@ _BROWSER_TEST_FILES = \
 	browser_476161_sample.html \
 	browser_480893.js \
 	browser_483330.js \
+	browser_485563.js \
 	$(NULL)
 
 libs:: $(_BROWSER_TEST_FILES)
diff --git a/browser/components/sessionstore/test/browser/browser_485563.js b/browser/components/sessionstore/test/browser/browser_485563.js
new file mode 100644
index 000000000000..1b24ecfd3966
--- /dev/null
+++ b/browser/components/sessionstore/test/browser/browser_485563.js
@@ -0,0 +1,59 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is sessionstore test code.
+ *
+ * The Initial Developer of the Original Code is
+ * Simon Bünzli <zeniko@gmail.com>.
+ * Portions created by the Initial Developer are Copyright (C) 2009
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+function test() {
+  /** Test for Bug 485563 **/
+  
+  let ss = Cc["@mozilla.org/browser/sessionstore;1"].getService(Ci.nsISessionStore);
+  waitForExplicitFinish();
+  
+  let uniqueValue = Math.random() + "\u2028Second line\u2029Second paragraph\u2027";
+  
+  let tab = gBrowser.addTab();
+  tab.linkedBrowser.addEventListener("load", function(aEvent) {
+    ss.setTabValue(tab, "bug485563", uniqueValue);
+    let tabState = eval("(" + ss.getTabState(tab) + ")");
+    is(tabState.extData["bug485563"], uniqueValue,
+       "unicode line separator wasn't over-encoded");
+    ss.deleteTabValue(tab, "bug485563");
+    ss.setTabState(tab, tabState.toSource());
+    is(ss.getTabValue(tab, "bug485563"), uniqueValue,
+       "unicode line separator was correctly preserved");
+    
+    gBrowser.removeTab(tab);
+    finish();
+  }, true);
+}