diff --git a/apps/openmw/mwworld/containerstore.cpp b/apps/openmw/mwworld/containerstore.cpp
index a3a4c14952..8d5ca4518c 100644
--- a/apps/openmw/mwworld/containerstore.cpp
+++ b/apps/openmw/mwworld/containerstore.cpp
@@ -192,6 +192,12 @@ int MWWorld::ContainerStore::count(const ESM::RefId& id) const
     return total;
 }
 
+void MWWorld::ContainerStore::clearRefNums()
+{
+    for (const auto& iter : *this)
+        iter.getCellRef().unsetRefNum();
+}
+
 MWWorld::ContainerStoreListener* MWWorld::ContainerStore::getContListener() const
 {
     return mListener;
diff --git a/apps/openmw/mwworld/containerstore.hpp b/apps/openmw/mwworld/containerstore.hpp
index e0fa3fecd7..9d02e0b95c 100644
--- a/apps/openmw/mwworld/containerstore.hpp
+++ b/apps/openmw/mwworld/containerstore.hpp
@@ -102,6 +102,10 @@ namespace MWWorld
     protected:
         ContainerStoreListener* mListener;
 
+        // Used in clone() to unset refnums of copies.
+        // (RefNum should be unique, copy can not have the same RefNum).
+        void clearRefNums();
+
         // (item, max charge)
         typedef std::vector<std::pair<ContainerStoreIterator, float>> TRechargingItems;
         TRechargingItems mRechargingItems;
@@ -165,7 +169,12 @@ namespace MWWorld
 
         virtual ~ContainerStore();
 
-        virtual std::unique_ptr<ContainerStore> clone() { return std::make_unique<ContainerStore>(*this); }
+        virtual std::unique_ptr<ContainerStore> clone()
+        {
+            auto res = std::make_unique<ContainerStore>(*this);
+            res->clearRefNums();
+            return res;
+        }
 
         ConstContainerStoreIterator cbegin(int mask = Type_All) const;
         ConstContainerStoreIterator cend() const;
diff --git a/apps/openmw/mwworld/inventorystore.hpp b/apps/openmw/mwworld/inventorystore.hpp
index a0c050e420..78d7e35275 100644
--- a/apps/openmw/mwworld/inventorystore.hpp
+++ b/apps/openmw/mwworld/inventorystore.hpp
@@ -97,7 +97,12 @@ namespace MWWorld
         const MWWorld::Ptr& getActor() const { return mActor; }
         void setActor(const MWWorld::Ptr& actor) { mActor = actor; }
 
-        std::unique_ptr<ContainerStore> clone() override { return std::make_unique<InventoryStore>(*this); }
+        std::unique_ptr<ContainerStore> clone() override
+        {
+            auto res = std::make_unique<InventoryStore>(*this);
+            res->clearRefNums();
+            return res;
+        }
 
         ContainerStoreIterator add(
             const Ptr& itemPtr, int count, bool allowAutoEquip = true, bool resolve = true) override;