diff --git a/apps/openmw/mwclass/activator.cpp b/apps/openmw/mwclass/activator.cpp
index 1ca1150df..fcf5dcfd7 100644
--- a/apps/openmw/mwclass/activator.cpp
+++ b/apps/openmw/mwclass/activator.cpp
@@ -45,11 +45,9 @@ namespace MWClass
         MWBase::Environment::get().getMechanicsManager()->add(ptr);
     }
 
-    std::string Activator::getModel(const MWWorld::Ptr &ptr) const
+    std::string Activator::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Activator> *ref =
-            ptr.get<ESM::Activator>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Activator> *ref = ptr.get<ESM::Activator>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/activator.hpp b/apps/openmw/mwclass/activator.hpp
index 4e371d8dd..7cdd9506c 100644
--- a/apps/openmw/mwclass/activator.hpp
+++ b/apps/openmw/mwclass/activator.hpp
@@ -39,7 +39,7 @@ namespace MWClass
 
             static void registerSelf();
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
     };
 }
 
diff --git a/apps/openmw/mwclass/apparatus.cpp b/apps/openmw/mwclass/apparatus.cpp
index 3caf68aae..6a64b88c2 100644
--- a/apps/openmw/mwclass/apparatus.cpp
+++ b/apps/openmw/mwclass/apparatus.cpp
@@ -37,11 +37,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Apparatus::getModel(const MWWorld::Ptr &ptr) const
+    std::string Apparatus::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Apparatus> *ref =
-            ptr.get<ESM::Apparatus>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Apparatus> *ref = ptr.get<ESM::Apparatus>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/apparatus.hpp b/apps/openmw/mwclass/apparatus.hpp
index 32b58af07..fbbe676eb 100644
--- a/apps/openmw/mwclass/apparatus.hpp
+++ b/apps/openmw/mwclass/apparatus.hpp
@@ -58,7 +58,7 @@ namespace MWClass
                 const;
             ///< Generate action for using via inventory menu
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual bool canSell (const MWWorld::Ptr& item, int npcServices) const;
     };
diff --git a/apps/openmw/mwclass/armor.cpp b/apps/openmw/mwclass/armor.cpp
index c9369e1ae..a4206a0be 100644
--- a/apps/openmw/mwclass/armor.cpp
+++ b/apps/openmw/mwclass/armor.cpp
@@ -43,11 +43,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Armor::getModel(const MWWorld::Ptr &ptr) const
+    std::string Armor::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Armor> *ref =
-            ptr.get<ESM::Armor>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Armor> *ref = ptr.get<ESM::Armor>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/armor.hpp b/apps/openmw/mwclass/armor.hpp
index c989fcde0..a2dd0adc7 100644
--- a/apps/openmw/mwclass/armor.hpp
+++ b/apps/openmw/mwclass/armor.hpp
@@ -81,7 +81,7 @@ namespace MWClass
                 const;
             ///< Generate action for using via inventory menu
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual int getEnchantmentPoints (const MWWorld::Ptr& ptr) const;
 
diff --git a/apps/openmw/mwclass/book.cpp b/apps/openmw/mwclass/book.cpp
index 49b53c480..f0e69eabf 100644
--- a/apps/openmw/mwclass/book.cpp
+++ b/apps/openmw/mwclass/book.cpp
@@ -40,11 +40,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Book::getModel(const MWWorld::Ptr &ptr) const
+    std::string Book::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Book> *ref =
-            ptr.get<ESM::Book>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Book> *ref = ptr.get<ESM::Book>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/book.hpp b/apps/openmw/mwclass/book.hpp
index a4f230219..38dc0ae7b 100644
--- a/apps/openmw/mwclass/book.hpp
+++ b/apps/openmw/mwclass/book.hpp
@@ -60,7 +60,7 @@ namespace MWClass
             virtual boost::shared_ptr<MWWorld::Action> use (const MWWorld::Ptr& ptr) const;
             ///< Generate action for using via inventory menu
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual int getEnchantmentPoints (const MWWorld::Ptr& ptr) const;
 
diff --git a/apps/openmw/mwclass/clothing.cpp b/apps/openmw/mwclass/clothing.cpp
index faa776e3a..ee75676bd 100644
--- a/apps/openmw/mwclass/clothing.cpp
+++ b/apps/openmw/mwclass/clothing.cpp
@@ -39,11 +39,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Clothing::getModel(const MWWorld::Ptr &ptr) const
+    std::string Clothing::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Clothing> *ref =
-            ptr.get<ESM::Clothing>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Clothing> *ref = ptr.get<ESM::Clothing>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/clothing.hpp b/apps/openmw/mwclass/clothing.hpp
index 30d16f0d7..655a38742 100644
--- a/apps/openmw/mwclass/clothing.hpp
+++ b/apps/openmw/mwclass/clothing.hpp
@@ -73,7 +73,7 @@ namespace MWClass
                 const;
             ///< Generate action for using via inventory menu
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual int getEnchantmentPoints (const MWWorld::Ptr& ptr) const;
 
diff --git a/apps/openmw/mwclass/container.cpp b/apps/openmw/mwclass/container.cpp
index 9c39c9df1..c70228bae 100644
--- a/apps/openmw/mwclass/container.cpp
+++ b/apps/openmw/mwclass/container.cpp
@@ -107,11 +107,9 @@ namespace MWClass
         MWBase::Environment::get().getMechanicsManager()->add(ptr);
     }
 
-    std::string Container::getModel(const MWWorld::Ptr &ptr) const
+    std::string Container::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Container> *ref =
-            ptr.get<ESM::Container>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Container> *ref = ptr.get<ESM::Container>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/container.hpp b/apps/openmw/mwclass/container.hpp
index 13593b1c0..c6a23df6c 100644
--- a/apps/openmw/mwclass/container.hpp
+++ b/apps/openmw/mwclass/container.hpp
@@ -73,7 +73,7 @@ namespace MWClass
 
             virtual void restock (const MWWorld::Ptr &ptr) const;
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
     };
 }
 
diff --git a/apps/openmw/mwclass/creature.cpp b/apps/openmw/mwclass/creature.cpp
index fceae4060..1072a2435 100644
--- a/apps/openmw/mwclass/creature.cpp
+++ b/apps/openmw/mwclass/creature.cpp
@@ -175,11 +175,9 @@ namespace MWClass
         objects.insertCreature(ptr, model, hasInventoryStore(ptr));
     }
 
-    std::string Creature::getModel(const MWWorld::Ptr &ptr) const
+    std::string Creature::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Creature> *ref =
-            ptr.get<ESM::Creature>();
-        assert (ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Creature> *ref = ptr.get<ESM::Creature>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/creature.hpp b/apps/openmw/mwclass/creature.hpp
index efb4715af..47e886c01 100644
--- a/apps/openmw/mwclass/creature.hpp
+++ b/apps/openmw/mwclass/creature.hpp
@@ -100,7 +100,7 @@ namespace MWClass
 
             static void registerSelf();
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual bool
             isActor() const {
diff --git a/apps/openmw/mwclass/door.cpp b/apps/openmw/mwclass/door.cpp
index 47116cd7b..3e6f2b956 100644
--- a/apps/openmw/mwclass/door.cpp
+++ b/apps/openmw/mwclass/door.cpp
@@ -78,11 +78,9 @@ namespace MWClass
         MWBase::Environment::get().getMechanicsManager()->add(ptr);
     }
 
-    std::string Door::getModel(const MWWorld::Ptr &ptr) const
+    std::string Door::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Door> *ref =
-            ptr.get<ESM::Door>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Door> *ref = ptr.get<ESM::Door>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/door.hpp b/apps/openmw/mwclass/door.hpp
index 384f38fa9..6cb297ca5 100644
--- a/apps/openmw/mwclass/door.hpp
+++ b/apps/openmw/mwclass/door.hpp
@@ -54,7 +54,7 @@ namespace MWClass
 
             static void registerSelf();
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             /// 0 = nothing, 1 = opening, 2 = closing
             virtual int getDoorState (const MWWorld::Ptr &ptr) const;
diff --git a/apps/openmw/mwclass/ingredient.cpp b/apps/openmw/mwclass/ingredient.cpp
index 95cf00d94..f871095c7 100644
--- a/apps/openmw/mwclass/ingredient.cpp
+++ b/apps/openmw/mwclass/ingredient.cpp
@@ -43,11 +43,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Ingredient::getModel(const MWWorld::Ptr &ptr) const
+    std::string Ingredient::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Ingredient> *ref =
-            ptr.get<ESM::Ingredient>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Ingredient> *ref = ptr.get<ESM::Ingredient>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/ingredient.hpp b/apps/openmw/mwclass/ingredient.hpp
index a6740a399..7f1e53ca6 100644
--- a/apps/openmw/mwclass/ingredient.hpp
+++ b/apps/openmw/mwclass/ingredient.hpp
@@ -55,7 +55,7 @@ namespace MWClass
             virtual std::string getInventoryIcon (const MWWorld::Ptr& ptr) const;
             ///< Return name of inventory icon.
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual float getWeight (const MWWorld::Ptr& ptr) const;
 
diff --git a/apps/openmw/mwclass/light.cpp b/apps/openmw/mwclass/light.cpp
index eb1c3bcc2..8c0a05b96 100644
--- a/apps/openmw/mwclass/light.cpp
+++ b/apps/openmw/mwclass/light.cpp
@@ -59,11 +59,9 @@ namespace MWClass
         MWBase::Environment::get().getMechanicsManager()->add(ptr);
     }
 
-    std::string Light::getModel(const MWWorld::Ptr &ptr) const
+    std::string Light::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Light> *ref =
-            ptr.get<ESM::Light>();
-        assert (ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Light> *ref = ptr.get<ESM::Light>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/light.hpp b/apps/openmw/mwclass/light.hpp
index 5e04fdb0b..3cc005429 100644
--- a/apps/openmw/mwclass/light.hpp
+++ b/apps/openmw/mwclass/light.hpp
@@ -65,7 +65,7 @@ namespace MWClass
             virtual float getRemainingUsageTime (const MWWorld::ConstPtr& ptr) const;
             ///< Returns the remaining duration of the object.
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual float getWeight (const MWWorld::Ptr& ptr) const;
 
diff --git a/apps/openmw/mwclass/lockpick.cpp b/apps/openmw/mwclass/lockpick.cpp
index 858a01992..53bcb9707 100644
--- a/apps/openmw/mwclass/lockpick.cpp
+++ b/apps/openmw/mwclass/lockpick.cpp
@@ -38,11 +38,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Lockpick::getModel(const MWWorld::Ptr &ptr) const
+    std::string Lockpick::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Lockpick> *ref =
-            ptr.get<ESM::Lockpick>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Lockpick> *ref = ptr.get<ESM::Lockpick>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/lockpick.hpp b/apps/openmw/mwclass/lockpick.hpp
index 44333eb45..565477b8b 100644
--- a/apps/openmw/mwclass/lockpick.hpp
+++ b/apps/openmw/mwclass/lockpick.hpp
@@ -59,7 +59,7 @@ namespace MWClass
                 const;
             ///< Generate action for using via inventory menu
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual bool canSell (const MWWorld::Ptr& item, int npcServices) const;
 
diff --git a/apps/openmw/mwclass/misc.cpp b/apps/openmw/mwclass/misc.cpp
index 57d5a1b1f..da8f48c38 100644
--- a/apps/openmw/mwclass/misc.cpp
+++ b/apps/openmw/mwclass/misc.cpp
@@ -51,11 +51,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Miscellaneous::getModel(const MWWorld::Ptr &ptr) const
+    std::string Miscellaneous::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Miscellaneous> *ref =
-            ptr.get<ESM::Miscellaneous>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Miscellaneous> *ref = ptr.get<ESM::Miscellaneous>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/misc.hpp b/apps/openmw/mwclass/misc.hpp
index a8ee52657..b2c7b5c76 100644
--- a/apps/openmw/mwclass/misc.hpp
+++ b/apps/openmw/mwclass/misc.hpp
@@ -51,7 +51,7 @@ namespace MWClass
             virtual std::string getInventoryIcon (const MWWorld::Ptr& ptr) const;
             ///< Return name of inventory icon.
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual boost::shared_ptr<MWWorld::Action> use (const MWWorld::Ptr& ptr)
                 const;
diff --git a/apps/openmw/mwclass/npc.cpp b/apps/openmw/mwclass/npc.cpp
index 0d0978d37..0dc97df87 100644
--- a/apps/openmw/mwclass/npc.cpp
+++ b/apps/openmw/mwclass/npc.cpp
@@ -425,11 +425,9 @@ namespace MWClass
         return ref->mBase->mPersistent;
     }
 
-    std::string Npc::getModel(const MWWorld::Ptr &ptr) const
+    std::string Npc::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::NPC> *ref =
-            ptr.get<ESM::NPC>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::NPC> *ref = ptr.get<ESM::NPC>();
 
         std::string model = "meshes\\base_anim.nif";
         const ESM::Race* race = MWBase::Environment::get().getWorld()->getStore().get<ESM::Race>().find(ref->mBase->mRace);
@@ -437,7 +435,6 @@ namespace MWClass
             model = "meshes\\base_animkna.nif";
 
         return model;
-
     }
 
     std::string Npc::getName (const MWWorld::ConstPtr& ptr) const
diff --git a/apps/openmw/mwclass/npc.hpp b/apps/openmw/mwclass/npc.hpp
index f5d9044a7..aac93ab6e 100644
--- a/apps/openmw/mwclass/npc.hpp
+++ b/apps/openmw/mwclass/npc.hpp
@@ -126,7 +126,7 @@ namespace MWClass
 
             static void registerSelf();
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual int getSkill(const MWWorld::Ptr& ptr, int skill) const;
 
diff --git a/apps/openmw/mwclass/potion.cpp b/apps/openmw/mwclass/potion.cpp
index 34f9922ea..7c499c7bc 100644
--- a/apps/openmw/mwclass/potion.cpp
+++ b/apps/openmw/mwclass/potion.cpp
@@ -41,11 +41,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Potion::getModel(const MWWorld::Ptr &ptr) const
+    std::string Potion::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Potion> *ref =
-            ptr.get<ESM::Potion>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Potion> *ref = ptr.get<ESM::Potion>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/potion.hpp b/apps/openmw/mwclass/potion.hpp
index 10083a7cf..d884277ce 100644
--- a/apps/openmw/mwclass/potion.hpp
+++ b/apps/openmw/mwclass/potion.hpp
@@ -54,7 +54,7 @@ namespace MWClass
             virtual std::string getInventoryIcon (const MWWorld::Ptr& ptr) const;
             ///< Return name of inventory icon.
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual float getWeight (const MWWorld::Ptr& ptr) const;
 
diff --git a/apps/openmw/mwclass/probe.cpp b/apps/openmw/mwclass/probe.cpp
index 8882af507..24d64c613 100644
--- a/apps/openmw/mwclass/probe.cpp
+++ b/apps/openmw/mwclass/probe.cpp
@@ -38,11 +38,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Probe::getModel(const MWWorld::Ptr &ptr) const
+    std::string Probe::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Probe> *ref =
-            ptr.get<ESM::Probe>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Probe> *ref = ptr.get<ESM::Probe>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/probe.hpp b/apps/openmw/mwclass/probe.hpp
index 69cf614fd..9a8c67789 100644
--- a/apps/openmw/mwclass/probe.hpp
+++ b/apps/openmw/mwclass/probe.hpp
@@ -59,7 +59,7 @@ namespace MWClass
                 const;
             ///< Generate action for using via inventory menu
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual bool canSell (const MWWorld::Ptr& item, int npcServices) const;
 
diff --git a/apps/openmw/mwclass/repair.cpp b/apps/openmw/mwclass/repair.cpp
index b52b06baf..038162c92 100644
--- a/apps/openmw/mwclass/repair.cpp
+++ b/apps/openmw/mwclass/repair.cpp
@@ -37,11 +37,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Repair::getModel(const MWWorld::Ptr &ptr) const
+    std::string Repair::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Repair> *ref =
-            ptr.get<ESM::Repair>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Repair> *ref = ptr.get<ESM::Repair>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/repair.hpp b/apps/openmw/mwclass/repair.hpp
index ed17ff587..b52677d68 100644
--- a/apps/openmw/mwclass/repair.hpp
+++ b/apps/openmw/mwclass/repair.hpp
@@ -51,7 +51,7 @@ namespace MWClass
             virtual std::string getInventoryIcon (const MWWorld::Ptr& ptr) const;
             ///< Return name of inventory icon.
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual boost::shared_ptr<MWWorld::Action> use (const MWWorld::Ptr& ptr)
                 const;
diff --git a/apps/openmw/mwclass/static.cpp b/apps/openmw/mwclass/static.cpp
index f9d9f618a..5539f8375 100644
--- a/apps/openmw/mwclass/static.cpp
+++ b/apps/openmw/mwclass/static.cpp
@@ -29,11 +29,9 @@ namespace MWClass
             physics.addObject(ptr, model);
     }
 
-    std::string Static::getModel(const MWWorld::Ptr &ptr) const
+    std::string Static::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Static> *ref =
-            ptr.get<ESM::Static>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Static> *ref = ptr.get<ESM::Static>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/static.hpp b/apps/openmw/mwclass/static.hpp
index 1748f86c6..9c4a61410 100644
--- a/apps/openmw/mwclass/static.hpp
+++ b/apps/openmw/mwclass/static.hpp
@@ -26,7 +26,7 @@ namespace MWClass
 
             static void registerSelf();
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
     };
 }
 
diff --git a/apps/openmw/mwclass/weapon.cpp b/apps/openmw/mwclass/weapon.cpp
index e363c942e..438497024 100644
--- a/apps/openmw/mwclass/weapon.cpp
+++ b/apps/openmw/mwclass/weapon.cpp
@@ -41,11 +41,9 @@ namespace MWClass
         // TODO: add option somewhere to enable collision for placeable objects
     }
 
-    std::string Weapon::getModel(const MWWorld::Ptr &ptr) const
+    std::string Weapon::getModel(const MWWorld::ConstPtr &ptr) const
     {
-        MWWorld::LiveCellRef<ESM::Weapon> *ref =
-            ptr.get<ESM::Weapon>();
-        assert(ref->mBase != NULL);
+        const MWWorld::LiveCellRef<ESM::Weapon> *ref = ptr.get<ESM::Weapon>();
 
         const std::string &model = ref->mBase->mModel;
         if (!model.empty()) {
diff --git a/apps/openmw/mwclass/weapon.hpp b/apps/openmw/mwclass/weapon.hpp
index 916b61eae..877de41d3 100644
--- a/apps/openmw/mwclass/weapon.hpp
+++ b/apps/openmw/mwclass/weapon.hpp
@@ -79,7 +79,7 @@ namespace MWClass
                 const;
             ///< Generate action for using via inventory menu
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual bool canSell (const MWWorld::Ptr& item, int npcServices) const;
 
diff --git a/apps/openmw/mwworld/class.cpp b/apps/openmw/mwworld/class.cpp
index 85a5a5720..2e6b74abc 100644
--- a/apps/openmw/mwworld/class.cpp
+++ b/apps/openmw/mwworld/class.cpp
@@ -291,7 +291,7 @@ namespace MWWorld
     {
     }
 
-    std::string Class::getModel(const MWWorld::Ptr &ptr) const
+    std::string Class::getModel(const MWWorld::ConstPtr &ptr) const
     {
         return "";
     }
diff --git a/apps/openmw/mwworld/class.hpp b/apps/openmw/mwworld/class.hpp
index 341094964..9d1190a04 100644
--- a/apps/openmw/mwworld/class.hpp
+++ b/apps/openmw/mwworld/class.hpp
@@ -266,7 +266,7 @@ namespace MWWorld
 
             virtual int getServices (const MWWorld::Ptr& actor) const;
 
-            virtual std::string getModel(const MWWorld::Ptr &ptr) const;
+            virtual std::string getModel(const MWWorld::ConstPtr &ptr) const;
 
             virtual std::string applyEnchantment(const MWWorld::Ptr &ptr, const std::string& enchId, int enchCharge, const std::string& newName) const;
             ///< Creates a new record using \a ptr as template, with the given name and the given enchantment applied to it.