Index: src/core/qgsmaprenderer.cpp
===================================================================
--- src/core/qgsmaprenderer.cpp	(revision 15676)
+++ src/core/qgsmaprenderer.cpp	(working copy)
@@ -838,10 +838,11 @@
   // We can't use a constructor since QgsRectangle normalizes the rectangle upon construction
   mFullExtent.setMinimal();
 
+  QList<QString> list = registry->mapLayers().keys();
   // iterate through the map layers and test each layers extent
   // against the current min and max values
-  QStringList::iterator it = mLayerSet.begin();
-  while ( it != mLayerSet.end() )
+  QStringList::iterator it = list.begin();
+  while ( it != list.end() )
   {
     QgsMapLayer * lyr = registry->mapLayer( *it );
     if ( lyr == NULL )
@@ -861,7 +862,7 @@
       mFullExtent.unionRect( extent );
 
     }
-    it++;
+    ++it;
   }
 
   if ( mFullExtent.width() == 0.0 || mFullExtent.height() == 0.0 )