--- a/js/xpconnect/src/XPCComponents.cpp
+++ b/js/xpconnect/src/XPCComponents.cpp
@@ -552,19 +552,20 @@ nsXPCComponents_InterfacesByID::NewResol
 
     if (!JSID_IS_STRING(id))
         return NS_OK;
 
     RootedString str(cx, JSID_TO_STRING(id));
     if (38 != JS_GetStringLength(str))
         return NS_OK;
 
-    if (const jschar *name = JS_GetInternedStringChars(str)) {
+    JSAutoByteString utf8str;
+    if (utf8str.encodeUtf8(cx, str)) {
         nsID iid;
-        if (!iid.Parse(NS_ConvertUTF16toUTF8(name).get()))
+        if (!iid.Parse(utf8str.ptr()))
             return NS_OK;
 
         nsCOMPtr<nsIInterfaceInfo> info;
         XPTInterfaceInfoManager::GetSingleton()->
             GetInfoForIID(&iid, getter_AddRefs(info));
         if (!info)
             return NS_OK;
 
@@ -2600,23 +2601,22 @@ nsXPCComponents_Utils::ReportError(Handl
 
     nsString fileName;
     int32_t lineNo = 0;
     if (frame) {
         frame->GetFilename(fileName);
         frame->GetLineNumber(&lineNo);
     }
 
-    const jschar *msgchars = JS_GetStringCharsZ(cx, msgstr);
-    if (!msgchars)
+    nsAutoJSString msg;
+    if (!msg.init(cx, msgstr))
         return NS_OK;
 
     nsresult rv = scripterr->InitWithWindowID(
-            nsDependentString(static_cast<const char16_t *>(msgchars)),
-            fileName, EmptyString(), lineNo, 0, 0,
+            msg, fileName, EmptyString(), lineNo, 0, 0,
             "XPConnect JavaScript", innerWindowID);
     NS_ENSURE_SUCCESS(rv, NS_OK);
 
     console->LogMessage(scripterr);
     return NS_OK;
 }
 
 /* void evalInSandbox(in AString source, in nativeobj sandbox); */

--- a/js/xpconnect/src/XPCWrappedJSClass.cpp
+++ b/js/xpconnect/src/XPCWrappedJSClass.cpp
@@ -363,23 +363,22 @@ nsXPCWrappedJSClass::BuildPropertyEnumer
         RootedValue jsvalName(cx);
         if (!JS_IdToValue(cx, idName, &jsvalName))
             return NS_ERROR_FAILURE;
 
         JSString* name = ToString(cx, jsvalName);
         if (!name)
             return NS_ERROR_FAILURE;
 
-        size_t length;
-        const jschar *chars = JS_GetStringCharsAndLength(cx, name, &length);
-        if (!chars)
+        nsAutoJSString autoStr;
+        if (!autoStr.init(cx, name))
             return NS_ERROR_FAILURE;
 
         nsCOMPtr<nsIProperty> property =
-            new xpcProperty(chars, (uint32_t) length, value);
+            new xpcProperty(autoStr.get(), (uint32_t)autoStr.Length(), value);
 
         if (!propertyArray.AppendObject(property))
             return NS_ERROR_FAILURE;
     }
 
     return NS_NewArrayEnumerator(aEnumerate, propertyArray);
 }