diff --git a/apps/essimporter/converter.cpp b/apps/essimporter/converter.cpp
index 4cf528c832..195b299450 100644
--- a/apps/essimporter/converter.cpp
+++ b/apps/essimporter/converter.cpp
@@ -491,7 +491,7 @@ namespace ESSImport
 
                 out.mSpellId = ESM::RefId::stringRefId(it->mSPDT.mId.toString());
                 out.mSpeed = pnam.mSpeed * 0.001f; // not sure where this factor comes from
-                out.mSlot = 0;
+                out.mItem = ESM::RefNum();
 
                 esm.startRecord(ESM::REC_MPRJ);
                 out.save(esm);
diff --git a/apps/openmw/mwbase/world.hpp b/apps/openmw/mwbase/world.hpp
index a57bb70134..a4f714973c 100644
--- a/apps/openmw/mwbase/world.hpp
+++ b/apps/openmw/mwbase/world.hpp
@@ -483,8 +483,8 @@ namespace MWBase
 
         virtual void castSpell(const MWWorld::Ptr& actor, bool manualSpell = false) = 0;
 
-        virtual void launchMagicBolt(
-            const ESM::RefId& spellId, const MWWorld::Ptr& caster, const osg::Vec3f& fallbackDirection, int slot)
+        virtual void launchMagicBolt(const ESM::RefId& spellId, const MWWorld::Ptr& caster,
+            const osg::Vec3f& fallbackDirection, ESM::RefNum item)
             = 0;
         virtual void launchProjectile(MWWorld::Ptr& actor, MWWorld::Ptr& projectile, const osg::Vec3f& worldPos,
             const osg::Quat& orient, MWWorld::Ptr& bow, float speed, float attackStrength)
diff --git a/apps/openmw/mwmechanics/activespells.cpp b/apps/openmw/mwmechanics/activespells.cpp
index ef5c9992be..55477bef0c 100644
--- a/apps/openmw/mwmechanics/activespells.cpp
+++ b/apps/openmw/mwmechanics/activespells.cpp
@@ -85,7 +85,7 @@ namespace MWMechanics
         : mId(cast.mId)
         , mDisplayName(cast.mSourceName)
         , mCasterActorId(-1)
-        , mSlot(cast.mSlot)
+        , mItem(cast.mItem)
         , mType(cast.mType)
         , mWorsenings(-1)
     {
@@ -98,7 +98,6 @@ namespace MWMechanics
         : mId(spell->mId)
         , mDisplayName(spell->mName)
         , mCasterActorId(actor.getClass().getCreatureStats(actor).getActorId())
-        , mSlot(0)
         , mType(spell->mData.mType == ESM::Spell::ST_Ability ? ESM::ActiveSpells::Type_Ability
                                                              : ESM::ActiveSpells::Type_Permanent)
         , mWorsenings(-1)
@@ -108,11 +107,11 @@ namespace MWMechanics
     }
 
     ActiveSpells::ActiveSpellParams::ActiveSpellParams(
-        const MWWorld::ConstPtr& item, const ESM::Enchantment* enchantment, int slotIndex, const MWWorld::Ptr& actor)
+        const MWWorld::ConstPtr& item, const ESM::Enchantment* enchantment, const MWWorld::Ptr& actor)
         : mId(item.getCellRef().getRefId())
         , mDisplayName(item.getClass().getName(item))
         , mCasterActorId(actor.getClass().getCreatureStats(actor).getActorId())
-        , mSlot(slotIndex)
+        , mItem(item.getCellRef().getRefNum())
         , mType(ESM::ActiveSpells::Type_Enchantment)
         , mWorsenings(-1)
     {
@@ -125,7 +124,7 @@ namespace MWMechanics
         , mEffects(params.mEffects)
         , mDisplayName(params.mDisplayName)
         , mCasterActorId(params.mCasterActorId)
-        , mSlot(params.mItem.isSet() ? params.mItem.mIndex : 0)
+        , mItem(params.mItem)
         , mType(params.mType)
         , mWorsenings(params.mWorsenings)
         , mNextWorsening({ params.mNextWorsening })
@@ -136,7 +135,7 @@ namespace MWMechanics
         : mId(params.mId)
         , mDisplayName(params.mDisplayName)
         , mCasterActorId(actor.getClass().getCreatureStats(actor).getActorId())
-        , mSlot(params.mSlot)
+        , mItem(params.mItem)
         , mType(params.mType)
         , mWorsenings(-1)
     {
@@ -149,12 +148,7 @@ namespace MWMechanics
         params.mEffects = mEffects;
         params.mDisplayName = mDisplayName;
         params.mCasterActorId = mCasterActorId;
-        if (mSlot)
-        {
-            // Note that we're storing the inventory slot as a RefNum instead of an int as a matter of future proofing
-            // mSlot needs to be replaced with a RefNum once inventory items get persistent RefNum (#4508 #6148)
-            params.mItem = { static_cast<unsigned int>(mSlot), 0 };
-        }
+        params.mItem = mItem;
         params.mType = mType;
         params.mWorsenings = mWorsenings;
         params.mNextWorsening = mNextWorsening.toEsm();
@@ -254,7 +248,8 @@ namespace MWMechanics
                         continue;
                     if (std::find_if(mSpells.begin(), mSpells.end(),
                             [&](const ActiveSpellParams& params) {
-                                return params.mSlot == slotIndex && params.mType == ESM::ActiveSpells::Type_Enchantment
+                                return params.mItem == slot->getCellRef().getRefNum()
+                                    && params.mType == ESM::ActiveSpells::Type_Enchantment
                                     && params.mId == slot->getCellRef().getRefId();
                             })
                         != mSpells.end())
@@ -264,7 +259,7 @@ namespace MWMechanics
                     purgeEffect(ptr, ESM::MagicEffect::Invisibility);
                     applyPurges(ptr);
                     const ActiveSpellParams& params
-                        = mSpells.emplace_back(ActiveSpellParams{ *slot, enchantment, slotIndex, ptr });
+                        = mSpells.emplace_back(ActiveSpellParams{ *slot, enchantment, ptr });
                     for (const auto& effect : params.mEffects)
                         MWMechanics::playEffects(
                             ptr, *world->getStore().get<ESM::MagicEffect>().find(effect.mEffectId), playNonLooping);
@@ -351,9 +346,19 @@ namespace MWMechanics
             }
             else if (spellIt->mType == ESM::ActiveSpells::Type_Enchantment)
             {
+                // Remove constant effect enchantments that have been unequipped
                 const auto& store = ptr.getClass().getInventoryStore(ptr);
-                auto slot = store.getSlot(spellIt->mSlot);
-                remove = slot == store.end() || slot->getCellRef().getRefId() != spellIt->mId;
+                remove = true;
+                for (int slotIndex = 0; slotIndex < MWWorld::InventoryStore::Slots; slotIndex++)
+                {
+                    auto slot = store.getSlot(slotIndex);
+                    if (slot != store.end() && slot->getCellRef().getRefNum().isSet()
+                        && slot->getCellRef().getRefNum() == spellIt->mItem)
+                    {
+                        remove = false;
+                        break;
+                    }
+                }
             }
             if (remove)
             {
@@ -382,7 +387,7 @@ namespace MWMechanics
         {
             auto found = std::find_if(mSpells.begin(), mSpells.end(), [&](const auto& existing) {
                 return spell.mId == existing.mId && spell.mCasterActorId == existing.mCasterActorId
-                    && spell.mSlot == existing.mSlot;
+                    && spell.mItem == existing.mItem;
             });
             if (found != mSpells.end())
             {
diff --git a/apps/openmw/mwmechanics/activespells.hpp b/apps/openmw/mwmechanics/activespells.hpp
index 6b71d93d64..8184567a5a 100644
--- a/apps/openmw/mwmechanics/activespells.hpp
+++ b/apps/openmw/mwmechanics/activespells.hpp
@@ -37,17 +37,18 @@ namespace MWMechanics
             std::vector<ActiveEffect> mEffects;
             std::string mDisplayName;
             int mCasterActorId;
-            int mSlot;
+            ESM::RefNum mItem;
             ESM::ActiveSpells::EffectType mType;
             int mWorsenings;
             MWWorld::TimeStamp mNextWorsening;
+            MWWorld::Ptr mSource;
 
             ActiveSpellParams(const ESM::ActiveSpells::ActiveSpellParams& params);
 
             ActiveSpellParams(const ESM::Spell* spell, const MWWorld::Ptr& actor, bool ignoreResistances = false);
 
-            ActiveSpellParams(const MWWorld::ConstPtr& item, const ESM::Enchantment* enchantment, int slotIndex,
-                const MWWorld::Ptr& actor);
+            ActiveSpellParams(
+                const MWWorld::ConstPtr& item, const ESM::Enchantment* enchantment, const MWWorld::Ptr& actor);
 
             ActiveSpellParams(const ActiveSpellParams& params, const MWWorld::Ptr& actor);
 
diff --git a/apps/openmw/mwmechanics/combat.cpp b/apps/openmw/mwmechanics/combat.cpp
index ef870b1edf..1c9c0c1dee 100644
--- a/apps/openmw/mwmechanics/combat.cpp
+++ b/apps/openmw/mwmechanics/combat.cpp
@@ -54,7 +54,7 @@ namespace MWMechanics
             {
                 MWMechanics::CastSpell cast(attacker, victim, fromProjectile);
                 cast.mHitPosition = hitPosition;
-                cast.cast(object, 0, false);
+                cast.cast(object, false);
                 // Apply magic effects directly instead of waiting a frame to allow soul trap to work on one-hit kills
                 if (!victim.isEmpty() && victim.getClass().isActor())
                     MWBase::Environment::get().getMechanicsManager()->updateMagicEffects(victim);
diff --git a/apps/openmw/mwmechanics/spellcasting.cpp b/apps/openmw/mwmechanics/spellcasting.cpp
index d7aa0d6b71..52e371b6e9 100644
--- a/apps/openmw/mwmechanics/spellcasting.cpp
+++ b/apps/openmw/mwmechanics/spellcasting.cpp
@@ -146,7 +146,7 @@ namespace MWMechanics
             fallbackDirection = (mTarget.getRefData().getPosition().asVec3() + offset)
                 - (mCaster.getRefData().getPosition().asVec3());
 
-        MWBase::Environment::get().getWorld()->launchMagicBolt(mId, mCaster, fallbackDirection, mSlot);
+        MWBase::Environment::get().getWorld()->launchMagicBolt(mId, mCaster, fallbackDirection, mItem);
     }
 
     void CastSpell::inflict(
@@ -290,7 +290,7 @@ namespace MWMechanics
         throw std::runtime_error("ID type cannot be casted");
     }
 
-    bool CastSpell::cast(const MWWorld::Ptr& item, int slot, bool launchProjectile)
+    bool CastSpell::cast(const MWWorld::Ptr& item, bool launchProjectile)
     {
         const ESM::RefId& enchantmentName = item.getClass().getEnchantment(item);
         if (enchantmentName.empty())
@@ -302,7 +302,10 @@ namespace MWMechanics
         const auto& store = MWBase::Environment::get().getESMStore();
         const ESM::Enchantment* enchantment = store->get<ESM::Enchantment>().find(enchantmentName);
 
-        mSlot = slot;
+        // CastOnce enchantments (i.e. scrolls) never stack and the item is immediately destroyed,
+        // so don't track the source item.
+        if (enchantment->mData.mType != ESM::Enchantment::CastOnce)
+            mItem = item.getCellRef().getRefNum();
 
         bool godmode = mCaster == MWMechanics::getPlayer() && MWBase::Environment::get().getWorld()->getGodModeState();
         bool isProjectile = false;
diff --git a/apps/openmw/mwmechanics/spellcasting.hpp b/apps/openmw/mwmechanics/spellcasting.hpp
index adad2de0e3..8f10066e04 100644
--- a/apps/openmw/mwmechanics/spellcasting.hpp
+++ b/apps/openmw/mwmechanics/spellcasting.hpp
@@ -43,7 +43,7 @@ namespace MWMechanics
         bool mFromProjectile; // True if spell is cast by enchantment of some projectile (arrow, bolt or thrown weapon)
         bool mManualSpell; // True if spell is casted from script and ignores some checks (mana level, success chance,
                            // etc.)
-        int mSlot{ 0 };
+        ESM::RefNum mItem;
         ESM::ActiveSpells::EffectType mType{ ESM::ActiveSpells::Type_Temporary };
 
         CastSpell(const MWWorld::Ptr& caster, const MWWorld::Ptr& target, const bool fromProjectile = false,
@@ -54,7 +54,7 @@ namespace MWMechanics
         /// @note mCaster must be an actor
         /// @param launchProjectile If set to false, "on target" effects are directly applied instead of being launched
         /// as projectile originating from the caster.
-        bool cast(const MWWorld::Ptr& item, int slot, bool launchProjectile = true);
+        bool cast(const MWWorld::Ptr& item, bool launchProjectile = true);
 
         /// @note mCaster must be an NPC
         bool cast(const ESM::Ingredient* ingredient);
diff --git a/apps/openmw/mwworld/containerstore.cpp b/apps/openmw/mwworld/containerstore.cpp
index b3ea654404..f5e45415ae 100644
--- a/apps/openmw/mwworld/containerstore.cpp
+++ b/apps/openmw/mwworld/containerstore.cpp
@@ -104,8 +104,10 @@ MWWorld::ContainerStoreIterator MWWorld::ContainerStore::getState(
     LiveCellRef<T> ref(record);
     ref.load(state);
     collection.mList.push_back(ref);
+    auto it = ContainerStoreIterator(this, --collection.mList.end());
+    MWBase::Environment::get().getWorldModel()->registerPtr(*it);
 
-    return ContainerStoreIterator(this, --collection.mList.end());
+    return it;
 }
 
 void MWWorld::ContainerStore::storeEquipmentState(
@@ -155,7 +157,12 @@ MWWorld::ContainerStore::ContainerStore()
 {
 }
 
-MWWorld::ContainerStore::~ContainerStore() {}
+MWWorld::ContainerStore::~ContainerStore()
+{
+    MWWorld::WorldModel* worldModel = MWBase::Environment::get().getWorldModel();
+    for (MWWorld::ContainerStoreIterator iter(begin()); iter != end(); ++iter)
+        worldModel->deregisterPtr(*iter);
+}
 
 MWWorld::ConstContainerStoreIterator MWWorld::ContainerStore::cbegin(int mask) const
 {
@@ -196,10 +203,14 @@ int MWWorld::ContainerStore::count(const ESM::RefId& id) const
     return total;
 }
 
-void MWWorld::ContainerStore::clearRefNums()
+void MWWorld::ContainerStore::updateRefNums()
 {
     for (const auto& iter : *this)
+    {
         iter.getCellRef().unsetRefNum();
+        iter.getRefData().setLuaScripts(nullptr);
+        MWBase::Environment::get().getWorldModel()->registerPtr(iter);
+    }
 }
 
 MWWorld::ContainerStoreListener* MWWorld::ContainerStore::getContListener() const
@@ -656,7 +667,8 @@ void MWWorld::ContainerStore::addInitialItemImp(
     else
     {
         ptr.getCellRef().setOwner(owner);
-        addImp(ptr, count, false);
+        MWWorld::ContainerStoreIterator it = addImp(ptr, count, false);
+        MWBase::Environment::get().getWorldModel()->registerPtr(*it);
     }
 }
 
diff --git a/apps/openmw/mwworld/containerstore.hpp b/apps/openmw/mwworld/containerstore.hpp
index 1948c07ae5..c7ad14013b 100644
--- a/apps/openmw/mwworld/containerstore.hpp
+++ b/apps/openmw/mwworld/containerstore.hpp
@@ -117,7 +117,7 @@ namespace MWWorld
 
         // Used in clone() to unset refnums of copies.
         // (RefNum should be unique, copy can not have the same RefNum).
-        void clearRefNums();
+        void updateRefNums();
 
         // (item, max charge)
         typedef std::vector<std::pair<ContainerStoreIterator, float>> TRechargingItems;
@@ -185,7 +185,7 @@ namespace MWWorld
         virtual std::unique_ptr<ContainerStore> clone()
         {
             auto res = std::make_unique<ContainerStore>(*this);
-            res->clearRefNums();
+            res->updateRefNums();
             return res;
         }
 
diff --git a/apps/openmw/mwworld/inventorystore.hpp b/apps/openmw/mwworld/inventorystore.hpp
index 78d7e35275..c0723d319c 100644
--- a/apps/openmw/mwworld/inventorystore.hpp
+++ b/apps/openmw/mwworld/inventorystore.hpp
@@ -100,7 +100,7 @@ namespace MWWorld
         std::unique_ptr<ContainerStore> clone() override
         {
             auto res = std::make_unique<InventoryStore>(*this);
-            res->clearRefNums();
+            res->updateRefNums();
             return res;
         }
 
diff --git a/apps/openmw/mwworld/projectilemanager.cpp b/apps/openmw/mwworld/projectilemanager.cpp
index 4fdcb4de31..aef821fb1f 100644
--- a/apps/openmw/mwworld/projectilemanager.cpp
+++ b/apps/openmw/mwworld/projectilemanager.cpp
@@ -263,7 +263,7 @@ namespace MWWorld
     }
 
     void ProjectileManager::launchMagicBolt(
-        const ESM::RefId& spellId, const Ptr& caster, const osg::Vec3f& fallbackDirection, int slot)
+        const ESM::RefId& spellId, const Ptr& caster, const osg::Vec3f& fallbackDirection, ESM::RefNum item)
     {
         osg::Vec3f pos = caster.getRefData().getPosition().asVec3();
         if (caster.getClass().isActor())
@@ -287,7 +287,7 @@ namespace MWWorld
         MagicBoltState state;
         state.mSpellId = spellId;
         state.mCasterHandle = caster;
-        state.mSlot = slot;
+        state.mItem = item;
         if (caster.getClass().isActor())
             state.mActorId = caster.getClass().getCreatureStats(caster).getActorId();
         else
@@ -575,7 +575,7 @@ namespace MWWorld
             cast.mHitPosition = Misc::Convert::toOsg(projectile->getHitPosition());
             cast.mId = magicBoltState.mSpellId;
             cast.mSourceName = magicBoltState.mSourceName;
-            cast.mSlot = magicBoltState.mSlot;
+            cast.mItem = magicBoltState.mItem;
             // Grab original effect list so the indices are correct
             const ESM::EffectList* effects;
             if (const ESM::Spell* spell = esmStore.get<ESM::Spell>().search(magicBoltState.mSpellId))
@@ -669,7 +669,7 @@ namespace MWWorld
             state.mPosition = ESM::Vector3(osg::Vec3f(it->mNode->getPosition()));
             state.mOrientation = ESM::Quaternion(osg::Quat(it->mNode->getAttitude()));
             state.mActorId = it->mActorId;
-            state.mSlot = it->mSlot;
+            state.mItem = it->mItem;
             state.mSpellId = it->mSpellId;
             state.mSpeed = it->mSpeed;
 
@@ -727,7 +727,7 @@ namespace MWWorld
             state.mSpellId = esm.mSpellId;
             state.mActorId = esm.mActorId;
             state.mToDelete = false;
-            state.mSlot = esm.mSlot;
+            state.mItem = esm.mItem;
             std::string texture;
 
             try
diff --git a/apps/openmw/mwworld/projectilemanager.hpp b/apps/openmw/mwworld/projectilemanager.hpp
index 3e9d70893a..65254a9110 100644
--- a/apps/openmw/mwworld/projectilemanager.hpp
+++ b/apps/openmw/mwworld/projectilemanager.hpp
@@ -49,8 +49,8 @@ namespace MWWorld
             MWRender::RenderingManager* rendering, MWPhysics::PhysicsSystem* physics);
 
         /// If caster is an actor, the actor's facing orientation is used. Otherwise fallbackDirection is used.
-        void launchMagicBolt(
-            const ESM::RefId& spellId, const MWWorld::Ptr& caster, const osg::Vec3f& fallbackDirection, int slot);
+        void launchMagicBolt(const ESM::RefId& spellId, const MWWorld::Ptr& caster, const osg::Vec3f& fallbackDirection,
+            ESM::RefNum item);
 
         void launchProjectile(const MWWorld::Ptr& actor, const MWWorld::ConstPtr& projectile, const osg::Vec3f& pos,
             const osg::Quat& orient, const MWWorld::Ptr& bow, float speed, float attackStrength);
@@ -108,7 +108,8 @@ namespace MWWorld
             ESM::EffectList mEffects;
 
             float mSpeed;
-            int mSlot;
+            // Refnum of the casting item
+            ESM::RefNum mItem;
 
             std::vector<MWBase::Sound*> mSounds;
             std::set<ESM::RefId> mSoundIds;
diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index 6897d663e1..b78e7f4124 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -3136,9 +3136,9 @@ namespace MWWorld
     }
 
     void World::launchMagicBolt(
-        const ESM::RefId& spellId, const MWWorld::Ptr& caster, const osg::Vec3f& fallbackDirection, int slot)
+        const ESM::RefId& spellId, const MWWorld::Ptr& caster, const osg::Vec3f& fallbackDirection, ESM::RefNum item)
     {
-        mProjectileManager->launchMagicBolt(spellId, caster, fallbackDirection, slot);
+        mProjectileManager->launchMagicBolt(spellId, caster, fallbackDirection, item);
     }
 
     void World::updateProjectilesCasters()
diff --git a/apps/openmw/mwworld/worldimp.hpp b/apps/openmw/mwworld/worldimp.hpp
index 615172ef96..89754ae796 100644
--- a/apps/openmw/mwworld/worldimp.hpp
+++ b/apps/openmw/mwworld/worldimp.hpp
@@ -578,7 +578,7 @@ namespace MWWorld
         void castSpell(const MWWorld::Ptr& actor, bool manualSpell = false) override;
 
         void launchMagicBolt(const ESM::RefId& spellId, const MWWorld::Ptr& caster, const osg::Vec3f& fallbackDirection,
-            int slot) override;
+            ESM::RefNum item) override;
         void launchProjectile(MWWorld::Ptr& actor, MWWorld::Ptr& projectile, const osg::Vec3f& worldPos,
             const osg::Quat& orient, MWWorld::Ptr& bow, float speed, float attackStrength) override;
         void updateProjectilesCasters() override;
diff --git a/components/esm3/activespells.cpp b/components/esm3/activespells.cpp
index 97d56d1a2b..e2906f2399 100644
--- a/components/esm3/activespells.cpp
+++ b/components/esm3/activespells.cpp
@@ -56,7 +56,14 @@ namespace ESM
                 {
                     esm.getHNT(params.mType, "TYPE");
                     if (esm.peekNextSub("ITEM"))
-                        params.mItem = esm.getFormId(true, "ITEM");
+                    {
+                        if (format <= MaxActiveSpellSlotIndexFormatVersion)
+                            // Previous versions saved slot index in this record.
+                            // Ignore these values as we can't use them
+                            esm.getFormId(true, "ITEM");
+                        else
+                            params.mItem = esm.getFormId(true, "ITEM");
+                    }
                 }
                 if (esm.isNextSub("WORS"))
                 {
diff --git a/components/esm3/formatversion.hpp b/components/esm3/formatversion.hpp
index aa0de9b0b7..644298b00d 100644
--- a/components/esm3/formatversion.hpp
+++ b/components/esm3/formatversion.hpp
@@ -24,7 +24,8 @@ namespace ESM
     inline constexpr FormatVersion MaxSavedGameCellNameAsRefIdFormatVersion = 24;
     inline constexpr FormatVersion MaxNameIsRefIdOnlyFormatVersion = 25;
     inline constexpr FormatVersion MaxUseEsmCellIdFormatVersion = 26;
-    inline constexpr FormatVersion CurrentSaveGameFormatVersion = 27;
+    inline constexpr FormatVersion MaxActiveSpellSlotIndexFormatVersion = 27;
+    inline constexpr FormatVersion CurrentSaveGameFormatVersion = 28;
 }
 
 #endif
diff --git a/components/esm3/projectilestate.cpp b/components/esm3/projectilestate.cpp
index 2b9eccc3e8..e3003f2fd0 100644
--- a/components/esm3/projectilestate.cpp
+++ b/components/esm3/projectilestate.cpp
@@ -28,7 +28,8 @@ namespace ESM
 
         esm.writeHNRefId("SPEL", mSpellId);
         esm.writeHNT("SPED", mSpeed);
-        esm.writeHNT("SLOT", mSlot);
+        if (mItem.isSet())
+            esm.writeFormId(mItem, true, "ITEM");
     }
 
     void MagicBoltState::load(ESMReader& esm)
@@ -40,10 +41,10 @@ namespace ESM
             esm.skipHSub();
         EffectList().load(esm); // for backwards compatibility
         esm.getHNT(mSpeed, "SPED");
-        if (esm.getFormatVersion() <= MaxClearModifiersFormatVersion)
-            mSlot = 0;
-        else
-            esm.getHNT(mSlot, "SLOT");
+        if (esm.peekNextSub("ITEM"))
+            mItem = esm.getFormId(true, "ITEM");
+        if (esm.isNextSub("SLOT")) // for backwards compatibility
+            esm.skipHSub();
         if (esm.isNextSub("STCK")) // for backwards compatibility
             esm.skipHSub();
         if (esm.isNextSub("SOUN")) // for backwards compatibility
diff --git a/components/esm3/projectilestate.hpp b/components/esm3/projectilestate.hpp
index afb8047da9..7a7651f364 100644
--- a/components/esm3/projectilestate.hpp
+++ b/components/esm3/projectilestate.hpp
@@ -33,7 +33,7 @@ namespace ESM
     {
         RefId mSpellId;
         float mSpeed;
-        int mSlot;
+        RefNum mItem;
 
         void load(ESMReader& esm);
         void save(ESMWriter& esm) const;