diff --git a/CHANGELOG.md b/CHANGELOG.md
index db5cc57e33..b972226a48 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
     Bug #4816: GetWeaponDrawn returns 1 before weapon is attached
     Bug #5057: Weapon swing sound plays at same pitch whether it hits or misses
     Bug #5129: Stuttering animation on Centurion Archer
+    Bug #5371: Keyframe animation tracks are used for any file that begins with an X
     Bug #5714: Touch spells cast using ExplodeSpell don't always explode
     Bug #5849: Paralysis breaks landing
     Bug #5883: Immobile creatures don't cause water ripples
diff --git a/apps/openmw/mwclass/activator.cpp b/apps/openmw/mwclass/activator.cpp
index 679dd0b505..4922bb21d1 100644
--- a/apps/openmw/mwclass/activator.cpp
+++ b/apps/openmw/mwclass/activator.cpp
@@ -45,7 +45,7 @@ namespace MWClass
     {
         if (!model.empty())
         {
-            renderingInterface.getObjects().insertModel(ptr, model, true);
+            renderingInterface.getObjects().insertModel(ptr, model);
             ptr.getRefData().getBaseNode()->setNodeMask(MWRender::Mask_Static);
         }
     }
diff --git a/apps/openmw/mwclass/container.cpp b/apps/openmw/mwclass/container.cpp
index f656965ca5..6023e0192a 100644
--- a/apps/openmw/mwclass/container.cpp
+++ b/apps/openmw/mwclass/container.cpp
@@ -108,7 +108,7 @@ namespace MWClass
     {
         if (!model.empty())
         {
-            renderingInterface.getObjects().insertModel(ptr, model, true);
+            renderingInterface.getObjects().insertModel(ptr, model);
         }
     }
 
diff --git a/apps/openmw/mwclass/door.cpp b/apps/openmw/mwclass/door.cpp
index 7ede0eef92..cf2f19d681 100644
--- a/apps/openmw/mwclass/door.cpp
+++ b/apps/openmw/mwclass/door.cpp
@@ -57,7 +57,7 @@ namespace MWClass
     {
         if (!model.empty())
         {
-            renderingInterface.getObjects().insertModel(ptr, model, true);
+            renderingInterface.getObjects().insertModel(ptr, model);
             ptr.getRefData().getBaseNode()->setNodeMask(MWRender::Mask_Static);
         }
     }
diff --git a/apps/openmw/mwclass/light.cpp b/apps/openmw/mwclass/light.cpp
index cd833fe609..04d9a758c5 100644
--- a/apps/openmw/mwclass/light.cpp
+++ b/apps/openmw/mwclass/light.cpp
@@ -40,8 +40,7 @@ namespace MWClass
         MWWorld::LiveCellRef<ESM::Light>* ref = ptr.get<ESM::Light>();
 
         // Insert even if model is empty, so that the light is added
-        renderingInterface.getObjects().insertModel(
-            ptr, model, true, !(ref->mBase->mData.mFlags & ESM::Light::OffDefault));
+        renderingInterface.getObjects().insertModel(ptr, model, !(ref->mBase->mData.mFlags & ESM::Light::OffDefault));
     }
 
     void Light::insertObject(const MWWorld::Ptr& ptr, const std::string& model, const osg::Quat& rotation,
diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index a9de8dedc1..271a7218a1 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -23,6 +23,7 @@
 #include <components/esm3/loadgmst.hpp>
 #include <components/esm3/loadmgef.hpp>
 #include <components/misc/convert.hpp>
+#include <components/misc/resourcehelpers.hpp>
 #include <components/resource/bulletshapemanager.hpp>
 #include <components/resource/resourcesystem.hpp>
 #include <components/settings/settings.hpp>
@@ -642,15 +643,15 @@ namespace MWPhysics
 
     void PhysicsSystem::addActor(const MWWorld::Ptr& ptr, const std::string& mesh)
     {
-        osg::ref_ptr<const Resource::BulletShape> shape = mShapeManager->getShape(mesh);
+        std::string animationMesh = Misc::ResourceHelpers::correctActorModelPath(mesh, mResourceSystem->getVFS());
+        osg::ref_ptr<const Resource::BulletShape> shape = mShapeManager->getShape(animationMesh);
 
         // Try to get shape from basic model as fallback for creatures
         if (!ptr.getClass().isNpc() && shape && shape->mCollisionBox.mExtents.length2() == 0)
         {
-            const std::string fallbackModel = ptr.getClass().getModel(ptr);
-            if (fallbackModel != mesh)
+            if (animationMesh != mesh)
             {
-                shape = mShapeManager->getShape(fallbackModel);
+                shape = mShapeManager->getShape(mesh);
             }
         }
 
diff --git a/apps/openmw/mwrender/animation.cpp b/apps/openmw/mwrender/animation.cpp
index 919f8a9e8e..15af30de5d 100644
--- a/apps/openmw/mwrender/animation.cpp
+++ b/apps/openmw/mwrender/animation.cpp
@@ -609,7 +609,7 @@ namespace MWRender
     {
         std::string kfname = Misc::StringUtils::lowerCase(model);
 
-        if (kfname.size() > 4 && kfname.compare(kfname.size() - 4, 4, ".nif") == 0)
+        if (kfname.ends_with(".nif"))
             kfname.replace(kfname.size() - 4, 4, ".kf");
 
         addSingleAnimSource(kfname, baseModel);
diff --git a/apps/openmw/mwrender/creatureanimation.cpp b/apps/openmw/mwrender/creatureanimation.cpp
index a724da1f71..c275d6a312 100644
--- a/apps/openmw/mwrender/creatureanimation.cpp
+++ b/apps/openmw/mwrender/creatureanimation.cpp
@@ -17,7 +17,7 @@ namespace MWRender
 {
 
     CreatureAnimation::CreatureAnimation(
-        const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem)
+        const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem, bool animated)
         : ActorAnimation(ptr, osg::ref_ptr<osg::Group>(ptr.getRefData().getBaseNode()), resourceSystem)
     {
         MWWorld::LiveCellRef<ESM::Creature>* ref = mPtr.get<ESM::Creature>();
@@ -28,12 +28,14 @@ namespace MWRender
 
             if ((ref->mBase->mFlags & ESM::Creature::Bipedal))
                 addAnimSource(Settings::Manager::getString("xbaseanim", "Models"), model);
-            addAnimSource(model, model);
+
+            if (animated)
+                addAnimSource(model, model);
         }
     }
 
     CreatureWeaponAnimation::CreatureWeaponAnimation(
-        const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem)
+        const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem, bool animated)
         : ActorAnimation(ptr, osg::ref_ptr<osg::Group>(ptr.getRefData().getBaseNode()), resourceSystem)
         , mShowWeapons(false)
         , mShowCarriedLeft(false)
@@ -45,10 +47,10 @@ namespace MWRender
             setObjectRoot(model, true, false, true);
 
             if ((ref->mBase->mFlags & ESM::Creature::Bipedal))
-            {
                 addAnimSource(Settings::Manager::getString("xbaseanim", "Models"), model);
-            }
-            addAnimSource(model, model);
+
+            if (animated)
+                addAnimSource(model, model);
 
             mPtr.getClass().getInventoryStore(mPtr).setInvListener(this, mPtr);
 
diff --git a/apps/openmw/mwrender/creatureanimation.hpp b/apps/openmw/mwrender/creatureanimation.hpp
index 3342fb3967..05235e5191 100644
--- a/apps/openmw/mwrender/creatureanimation.hpp
+++ b/apps/openmw/mwrender/creatureanimation.hpp
@@ -15,7 +15,8 @@ namespace MWRender
     class CreatureAnimation : public ActorAnimation
     {
     public:
-        CreatureAnimation(const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem);
+        CreatureAnimation(
+            const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem, bool animated);
         virtual ~CreatureAnimation() {}
     };
 
@@ -28,7 +29,7 @@ namespace MWRender
     {
     public:
         CreatureWeaponAnimation(
-            const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem);
+            const MWWorld::Ptr& ptr, const std::string& model, Resource::ResourceSystem* resourceSystem, bool animated);
         virtual ~CreatureWeaponAnimation() {}
 
         void equipmentChanged() override { updateParts(); }
diff --git a/apps/openmw/mwrender/objects.cpp b/apps/openmw/mwrender/objects.cpp
index 2d42623bd2..ba4ab45c60 100644
--- a/apps/openmw/mwrender/objects.cpp
+++ b/apps/openmw/mwrender/objects.cpp
@@ -3,6 +3,7 @@
 #include <osg/Group>
 #include <osg/UserDataContainer>
 
+#include <components/misc/resourcehelpers.hpp>
 #include <components/sceneutil/positionattitudetransform.hpp>
 #include <components/sceneutil/unrefqueue.hpp>
 
@@ -68,12 +69,21 @@ namespace MWRender
         ptr.getRefData().setBaseNode(insert);
     }
 
-    void Objects::insertModel(const MWWorld::Ptr& ptr, const std::string& mesh, bool animated, bool allowLight)
+    void Objects::insertModel(const MWWorld::Ptr& ptr, const std::string& mesh, bool allowLight)
     {
         insertBegin(ptr);
         ptr.getRefData().getBaseNode()->setNodeMask(Mask_Object);
+        bool animated = ptr.getClass().useAnim();
+        std::string animationMesh = mesh;
+        if (animated && !mesh.empty())
+        {
+            animationMesh = Misc::ResourceHelpers::correctActorModelPath(mesh, mResourceSystem->getVFS());
+            if (animationMesh == mesh)
+                animated = false;
+        }
 
-        osg::ref_ptr<ObjectAnimation> anim(new ObjectAnimation(ptr, mesh, mResourceSystem, animated, allowLight));
+        osg::ref_ptr<ObjectAnimation> anim(
+            new ObjectAnimation(ptr, animationMesh, mResourceSystem, animated, allowLight));
 
         mObjects.emplace(ptr.mRef, std::move(anim));
     }
@@ -83,13 +93,18 @@ namespace MWRender
         insertBegin(ptr);
         ptr.getRefData().getBaseNode()->setNodeMask(Mask_Actor);
 
+        bool animated = true;
+        std::string animationMesh = Misc::ResourceHelpers::correctActorModelPath(mesh, mResourceSystem->getVFS());
+        if (animationMesh == mesh)
+            animated = false;
+
         // CreatureAnimation
         osg::ref_ptr<Animation> anim;
 
         if (weaponsShields)
-            anim = new CreatureWeaponAnimation(ptr, mesh, mResourceSystem);
+            anim = new CreatureWeaponAnimation(ptr, animationMesh, mResourceSystem, animated);
         else
-            anim = new CreatureAnimation(ptr, mesh, mResourceSystem);
+            anim = new CreatureAnimation(ptr, animationMesh, mResourceSystem, animated);
 
         if (mObjects.emplace(ptr.mRef, anim).second)
             ptr.getClass().getContainerStore(ptr).setContListener(static_cast<ActorAnimation*>(anim.get()));
diff --git a/apps/openmw/mwrender/objects.hpp b/apps/openmw/mwrender/objects.hpp
index 339079cb0a..b4359fdb99 100644
--- a/apps/openmw/mwrender/objects.hpp
+++ b/apps/openmw/mwrender/objects.hpp
@@ -72,10 +72,8 @@ namespace MWRender
             SceneUtil::UnrefQueue& unrefQueue);
         ~Objects();
 
-        /// @param animated Attempt to load separate keyframes from a .kf file matching the model file?
         /// @param allowLight If false, no lights will be created, and particles systems will be removed.
-        void insertModel(
-            const MWWorld::Ptr& ptr, const std::string& model, bool animated = false, bool allowLight = true);
+        void insertModel(const MWWorld::Ptr& ptr, const std::string& model, bool allowLight = true);
 
         void insertNPC(const MWWorld::Ptr& ptr);
         void insertCreature(const MWWorld::Ptr& ptr, const std::string& model, bool weaponsShields);
diff --git a/apps/openmw/mwworld/scene.cpp b/apps/openmw/mwworld/scene.cpp
index e5c28a381b..0c8b56ec30 100644
--- a/apps/openmw/mwworld/scene.cpp
+++ b/apps/openmw/mwworld/scene.cpp
@@ -90,15 +90,11 @@ namespace
             rendering.rotateObject(ptr, rotation);
     }
 
-    std::string getModel(const MWWorld::Ptr& ptr, const VFS::Manager* vfs)
+    std::string getModel(const MWWorld::Ptr& ptr)
     {
         if (Misc::ResourceHelpers::isHiddenMarker(ptr.getCellRef().getRefId()))
             return {};
-        bool useAnim = ptr.getClass().useAnim();
-        std::string model = ptr.getClass().getModel(ptr);
-        if (useAnim)
-            model = Misc::ResourceHelpers::correctActorModelPath(model, vfs);
-        return model;
+        return ptr.getClass().getModel(ptr);
     }
 
     void addObject(const MWWorld::Ptr& ptr, const MWWorld::World& world, const std::vector<ESM::RefNum>& pagedRefs,
@@ -110,7 +106,7 @@ namespace
             return;
         }
 
-        std::string model = getModel(ptr, rendering.getResourceSystem()->getVFS());
+        std::string model = getModel(ptr);
         const auto rotation = makeDirectNodeRotation(ptr);
 
         const ESM::RefNum& refnum = ptr.getCellRef().getRefNum();
@@ -279,8 +275,7 @@ namespace MWWorld
         {
             if (!ptr.getRefData().getBaseNode())
                 return;
-            ptr.getClass().insertObjectRendering(
-                ptr, getModel(ptr, mRendering.getResourceSystem()->getVFS()), mRendering);
+            ptr.getClass().insertObjectRendering(ptr, getModel(ptr), mRendering);
             setNodeRotation(ptr, mRendering, makeNodeRotation(ptr, RotationOrder::direct));
             reloadTerrain();
         }
@@ -630,7 +625,7 @@ namespace MWWorld
                     ptr.mRef->mData.mPhysicsPostponed = false;
                     if (ptr.mRef->mData.isEnabled() && ptr.mRef->mData.getCount() > 0)
                     {
-                        std::string model = getModel(ptr, MWBase::Environment::get().getResourceSystem()->getVFS());
+                        std::string model = getModel(ptr);
                         if (!model.empty())
                         {
                             const auto rotation = makeNodeRotation(ptr, RotationOrder::direct);
diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index bd0d665a64..34c39fed82 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -2430,10 +2430,8 @@ namespace MWWorld
         MWBase::Environment::get().getMechanicsManager()->add(getPlayerPtr());
         MWBase::Environment::get().getWindowManager()->watchActor(getPlayerPtr());
 
-        std::string model = getPlayerPtr().getClass().getModel(getPlayerPtr());
-        model = Misc::ResourceHelpers::correctActorModelPath(model, mResourceSystem->getVFS());
         mPhysics->remove(getPlayerPtr());
-        mPhysics->addActor(getPlayerPtr(), model);
+        mPhysics->addActor(getPlayerPtr(), getPlayerPtr().getClass().getModel(getPlayerPtr()));
 
         applyLoopingParticles(player);
 
diff --git a/components/misc/resourcehelpers.cpp b/components/misc/resourcehelpers.cpp
index d172b4b8c9..c3f1a447bd 100644
--- a/components/misc/resourcehelpers.cpp
+++ b/components/misc/resourcehelpers.cpp
@@ -134,7 +134,11 @@ std::string Misc::ResourceHelpers::correctActorModelPath(const std::string& resP
         mdlname.insert(mdlname.begin() + p + 1, 'x');
     else
         mdlname.insert(mdlname.begin(), 'x');
-    if (!vfs->exists(mdlname))
+    std::string kfname = mdlname;
+    if (kfname.ends_with(".nif"))
+        kfname.replace(kfname.size() - 4, 4, ".kf");
+
+    if (!vfs->exists(kfname))
     {
         return resPath;
     }
diff --git a/components/misc/resourcehelpers.hpp b/components/misc/resourcehelpers.hpp
index bc11064654..079171c505 100644
--- a/components/misc/resourcehelpers.hpp
+++ b/components/misc/resourcehelpers.hpp
@@ -28,7 +28,8 @@ namespace Misc
         std::string correctIconPath(std::string_view resPath, const VFS::Manager* vfs);
         std::string correctBookartPath(std::string_view resPath, const VFS::Manager* vfs);
         std::string correctBookartPath(std::string_view resPath, int width, int height, const VFS::Manager* vfs);
-        /// Use "xfoo.nif" instead of "foo.nif" if available
+        /// Use "xfoo.nif" instead of "foo.nif" if "xfoo.kf" is available
+        /// Note that if "xfoo.nif" is actually unavailable, we can't fall back to "foo.nif". :(
         std::string correctActorModelPath(const std::string& resPath, const VFS::Manager* vfs);
         std::string correctMeshPath(const std::string& resPath, const VFS::Manager* vfs);
 
diff --git a/components/nifbullet/bulletnifloader.cpp b/components/nifbullet/bulletnifloader.cpp
index 56f59451fa..f276df0863 100644
--- a/components/nifbullet/bulletnifloader.cpp
+++ b/components/nifbullet/bulletnifloader.cpp
@@ -208,6 +208,7 @@ namespace NifBullet
         }
         // files with the name convention xmodel.nif usually have keyframes stored in a separate file xmodel.kf (see
         // Animation::addAnimSource). assume all nodes in the file will be animated
+        // TODO: investigate whether this should and could be optimized.
         const bool isAnimated = pathFileNameStartsWithX(filename);
 
         // If there's no bounding box, we'll have to generate a Bullet collision shape