diff --git a/src/osgTerrain/GeometryTechnique.cpp b/src/osgTerrain/GeometryTechnique.cpp
index d386e1aa5..0b326b865 100644
--- a/src/osgTerrain/GeometryTechnique.cpp
+++ b/src/osgTerrain/GeometryTechnique.cpp
@@ -903,7 +903,7 @@ void GeometryTechnique::generateGeometry(BufferData& buffer, Locator* masterLoca
 
         _neighbours.clear();
 
-        bool updateNeighboursImmediately = true;
+        bool updateNeighboursImmediately = false;
 
         if (left_tile.valid())   addNeighbour(left_tile.get());
         if (right_tile.valid())  addNeighbour(right_tile.get());
diff --git a/src/osgTerrain/Terrain.cpp b/src/osgTerrain/Terrain.cpp
index f5ae4257b..a0f0d0919 100644
--- a/src/osgTerrain/Terrain.cpp
+++ b/src/osgTerrain/Terrain.cpp
@@ -84,15 +84,21 @@ void Terrain::traverse(osg::NodeVisitor& nv)
         osgUtil::UpdateVisitor* uv = dynamic_cast<osgUtil::UpdateVisitor*>(&nv);
         if (uv)
         {
-            OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
-            for(TerrainTileSet::iterator itr = _updateTerrainTileSet.begin();
-                itr != _updateTerrainTileSet.end();
+            typedef std::list< osg::ref_ptr<TerrainTile> >  TerrainTileList;
+            TerrainTileList tiles;
+            {
+                OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+                std::copy(_updateTerrainTileSet.begin(), _updateTerrainTileSet.end(), std::back_inserter(tiles));
+                _updateTerrainTileSet.clear();
+            }
+
+            for(TerrainTileList::iterator itr = tiles.begin();
+                itr != tiles.end();
                 ++itr)
             {
                 TerrainTile* tile = *itr;
                 tile->traverse(nv);
             }
-            _updateTerrainTileSet.clear();
         }
     }