diff --git a/language/codecompletion/codecompletionitemgrouper.h b/language/codecompletion/codecompletionitemgrouper.h
index 1aca7fd411..e2fb7c9350 100644
--- a/language/codecompletion/codecompletionitemgrouper.h
+++ b/language/codecompletion/codecompletionitemgrouper.h
@@ -1,109 +1,112 @@
 /*
  * KDevelop Generic Code Completion Support
  *
  * Copyright 2006-2008 Hamish Rodda <rodda@kde.org>
  * Copyright 2007-2008 David Nolden <david.nolden.kdevelop@art-master.de>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU Library General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public
  * License along with this program; if not, write to the
  * Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
 #ifndef KDEV_CODECOMPLETIONITEMGROUPER_H
 #define KDEV_CODECOMPLETIONITEMGROUPER_H
 
 #include "codecompletionmodel.h"
 #include "codecompletionitem.h"
+#include <duchain/duchain.h>
+#include <duchain/duchainlock.h>
 
 namespace KDevelop {
 
 ///Always the last item of a grouping chain: Only inserts the items
 struct CodeCompletionItemLastGrouper {
   CodeCompletionItemLastGrouper(QList<KSharedPtr<CompletionTreeElement> >& tree, CompletionTreeNode* parent, QList<CompletionTreeItemPointer> items)
   {
     foreach( CompletionTreeItemPointer item, items ) {
       item->setParent(parent);
       tree << KSharedPtr<CompletionTreeElement>( item.data() );
     }
   }
 };
 
 ///Helper class that helps us grouping the completion-list. A chain of groupers can be built, by using NextGrouper.
 template<class KeyExtractor, class NextGrouper = CodeCompletionItemLastGrouper>
 struct CodeCompletionItemGrouper {
   typedef typename KeyExtractor::KeyType KeyType;
 
   CodeCompletionItemGrouper(QList<KSharedPtr<CompletionTreeElement> >& tree, CompletionTreeNode* parent, QList<CompletionTreeItemPointer> items)
   {
     typedef QMap<KeyType, QList<CompletionTreeItemPointer> > GroupMap;
     GroupMap groups;
 
     foreach(const CompletionTreeItemPointer& item, items) {
       KeyType key = KeyExtractor::extract(item);
       typename GroupMap::iterator it = groups.find(key);
       if(it == groups.end())
         it = groups.insert(key, QList<CompletionTreeItemPointer>());
 
       (*it).append(item);
     }
 
     for( typename GroupMap::const_iterator it = groups.constBegin(); it != groups.constEnd(); ++it ) {
       KSharedPtr<CompletionTreeNode> node(new CompletionTreeNode());
       node->setParent(parent);
       node->role = (KTextEditor::CodeCompletionModel::ExtraItemDataRoles)KeyExtractor::Role;
       node->roleValue = QVariant(it.key());
 
       tree << KSharedPtr<CompletionTreeElement>( node.data() );
       
       NextGrouper nextGrouper(node->children, node.data(), *it);
     }
   }
 };
 
 ///Extracts the argument-hint depth from completion-items, to be used in ItemGrouper for grouping by argument-hint depth.
 struct ArgumentHintDepthExtractor {
   typedef int KeyType;
   enum { Role = KTextEditor::CodeCompletionModel::ArgumentHintDepth };
   
   static KeyType extract( const CompletionTreeItemPointer& item ) {
     return item->argumentHintDepth();
   }
 };
 
 struct InheritanceDepthExtractor {
   typedef int KeyType;
   
   enum { Role = KTextEditor::CodeCompletionModel::InheritanceDepth };
   
   static KeyType extract( const CompletionTreeItemPointer& item ) {
     return item->inheritanceDepth();
   }
 };
 
 struct SimplifiedAttributesExtractor {
   typedef int KeyType;
   
   enum { Role = KTextEditor::CodeCompletionModel::CompletionRole };
 
   static int groupingProperties;
   
   static KeyType extract( const CompletionTreeItemPointer& item ) {
+      DUChainReadLocker lock(DUChain::lock());
       return item->completionProperties() & groupingProperties;
   }
 };
 
 
 }
 
 #endif // KDEV_CODECOMPLETIONITEMGROUPER_H