diff --git a/apps/openmw/mwbase/world.hpp b/apps/openmw/mwbase/world.hpp
index 06a8ffa35..c2a7de72b 100644
--- a/apps/openmw/mwbase/world.hpp
+++ b/apps/openmw/mwbase/world.hpp
@@ -141,7 +141,7 @@ namespace MWBase
 
             virtual bool isCellQuasiExterior() const = 0;
 
-            virtual osg::Vec2f getNorthVector (MWWorld::CellStore* cell) = 0;
+            virtual osg::Vec2f getNorthVector (const MWWorld::CellStore* cell) = 0;
             ///< get north vector for given interior cell
 
             virtual void getDoorMarkers (MWWorld::CellStore* cell, std::vector<DoorMarker>& out) = 0;
diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index 37743bceb..a556aabf7 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -1710,9 +1710,9 @@ namespace MWWorld
         mWeatherManager->modRegion(regionid, chances);
     }
 
-    osg::Vec2f World::getNorthVector (CellStore* cell)
+    osg::Vec2f World::getNorthVector (const CellStore* cell)
     {
-        MWWorld::Ptr northmarker = cell->search("northmarker");
+        MWWorld::ConstPtr northmarker = cell->searchConst("northmarker");
 
         if (northmarker.isEmpty())
             return osg::Vec2f(0, 1);
diff --git a/apps/openmw/mwworld/worldimp.hpp b/apps/openmw/mwworld/worldimp.hpp
index a9dce46e8..487d4ed04 100644
--- a/apps/openmw/mwworld/worldimp.hpp
+++ b/apps/openmw/mwworld/worldimp.hpp
@@ -227,7 +227,7 @@ namespace MWWorld
 
             virtual bool isCellQuasiExterior() const;
 
-            virtual osg::Vec2f getNorthVector (CellStore* cell);
+            virtual osg::Vec2f getNorthVector (const CellStore* cell);
             ///< get north vector for given interior cell
 
             virtual void getDoorMarkers (MWWorld::CellStore* cell, std::vector<DoorMarker>& out);