diff --git a/lib/hkStubs/CMakeLists.txt b/lib/hkStubs/CMakeLists.txt
index ebde6b0f..495e717e 100644
--- a/lib/hkStubs/CMakeLists.txt
+++ b/lib/hkStubs/CMakeLists.txt
@@ -95,6 +95,7 @@ add_library(hkStubs OBJECT
   Havok/Physics2012/Collide/Shape/Query/hkpShapeRayCastInput.h
   Havok/Physics2012/Collide/Util/Welding/hkpWeldingUtility.h
 
+  Havok/Physics2012/Dynamics/Collide/hkpResponseModifier.h
   Havok/Physics2012/Dynamics/Common/hkpMaterial.h
   Havok/Physics2012/Dynamics/Common/hkpProperty.h
   Havok/Physics2012/Dynamics/Entity/hkpEntity.h
diff --git a/lib/hkStubs/Havok/Physics2012/Dynamics/Collide/hkpResponseModifier.h b/lib/hkStubs/Havok/Physics2012/Dynamics/Collide/hkpResponseModifier.h
new file mode 100644
index 00000000..0fe06e79
--- /dev/null
+++ b/lib/hkStubs/Havok/Physics2012/Dynamics/Collide/hkpResponseModifier.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include <Havok/Common/Base/hkBase.h>
+
+class hkpConstraintInstance;
+class hkpConstraintOwner;
+class hkpDynamicsContactMgr;
+class hkpRigidBody;
+
+class hkpResponseModifier {
+public:
+    enum Flags {
+        MASS_SCALING = 1,
+        CENTER_OF_MASS_DISPLACEMENT = 2,
+        SURFACE_VELOCITY = 4,
+        IMPULSE_SCALING = 8,
+        VISCOUS_SURFACE = 16,
+
+        ADDITIONAL_SIZE_MODIFIERS = MASS_SCALING | CENTER_OF_MASS_DISPLACEMENT | SURFACE_VELOCITY,
+    };
+
+    static void setInvMassScalingForContact(hkpDynamicsContactMgr* manager, hkpRigidBody* bodyA,
+                                            hkpRigidBody* bodyB,
+                                            hkpConstraintOwner& constraintOwner,
+                                            const hkVector4& factorA, const hkVector4& factorB);
+
+    static void setInvMassScalingForContact(hkpDynamicsContactMgr* manager, hkpRigidBody* body,
+                                            hkpConstraintOwner& constraintOwner,
+                                            const hkVector4& factor);
+
+    static void setCenterOfMassDisplacementForContact(hkpDynamicsContactMgr* manager,
+                                                      hkpRigidBody* bodyA, hkpRigidBody* bodyB,
+                                                      hkpConstraintOwner& constraintOwner,
+                                                      const hkVector4& displacementA,
+                                                      const hkVector4& displacementB);
+
+    static void setImpulseScalingForContact(hkpDynamicsContactMgr* manager, hkpRigidBody* bodyA,
+                                            hkpRigidBody* bodyB,
+                                            hkpConstraintOwner& constraintOwner,
+                                            hkReal usedImpulseFraction, hkReal maxAcceleration);
+
+    static void setSurfaceVelocity(hkpDynamicsContactMgr* manager, hkpRigidBody* body,
+                                   hkpConstraintOwner& constraintOwner, const hkVector4& velWorld);
+
+    static void clearSurfaceVelocity(hkpDynamicsContactMgr* manager,
+                                     hkpConstraintOwner& constraintOwner, hkpRigidBody* body);
+
+    static void setLowSurfaceViscosity(hkpDynamicsContactMgr* manager,
+                                       hkpConstraintOwner& constraintOwner);
+
+    static void disableConstraint(hkpConstraintInstance* instance,
+                                  hkpConstraintOwner& constraintOwner);
+
+    static void enableConstraint(hkpConstraintInstance* instance,
+                                 hkpConstraintOwner& constraintOwner);
+
+    HK_FORCE_INLINE static hkUint16 getAdditionalSchemaSize(hkUint8 flags);
+
+    static const hkUint16 tableOfAdditionalSchemaSizes[];
+};
+
+inline hkUint16 hkpResponseModifier::getAdditionalSchemaSize(hkUint8 flags) {
+    return tableOfAdditionalSchemaSizes[flags & ADDITIONAL_SIZE_MODIFIERS];
+}
diff --git a/src/KingSystem/Physics/RigidBody/physRigidBody.cpp b/src/KingSystem/Physics/RigidBody/physRigidBody.cpp
index e228cde2..19f4a29a 100644
--- a/src/KingSystem/Physics/RigidBody/physRigidBody.cpp
+++ b/src/KingSystem/Physics/RigidBody/physRigidBody.cpp
@@ -1,4 +1,5 @@
 #include "KingSystem/Physics/RigidBody/physRigidBody.h"
+#include <Havok/Physics2012/Dynamics/Collide/hkpResponseModifier.h>
 #include <Havok/Physics2012/Dynamics/Entity/hkpRigidBody.h>
 #include "KingSystem/Physics/System/physMemSystem.h"
 
@@ -17,7 +18,7 @@ RigidBody::RigidBody(u32 a, u32 mass_scaling, hkpRigidBody* hk_body, const sead:
     mHkBody->enableDeactivation(true);
     mHkBody->getCollidableRw()->m_allowedPenetrationDepth = 0.1f;
     if (mFlags.isOff(Flag1::MassScaling)) {
-        mHkBody->m_responseModifierFlags |= 1;
+        mHkBody->m_responseModifierFlags |= hkpResponseModifier::Flags::MASS_SCALING;
     }
 
     mFlags.change(Flag1::_80, _b4 == 5);