diff --git a/irr/include/SkinnedMesh.h b/irr/include/SkinnedMesh.h
index 5a1a9c4c8..fbfd29aa8 100644
--- a/irr/include/SkinnedMesh.h
+++ b/irr/include/SkinnedMesh.h
@@ -75,7 +75,7 @@ public:
 
 	//! Turns the given array of local matrices into an array of global matrices
 	//! by multiplying with respective parent matrices.
-	void calculateGlobalMatrices(std::vector<core::matrix4> &matrices);
+	void calculateGlobalMatrices(std::vector<core::matrix4> &matrices) const;
 
 	//! Performs a software skin on this mesh based on the given joint matrices
 	void skinMesh(const std::vector<core::matrix4> &animated_transforms);
diff --git a/irr/src/CXMeshFileLoader.cpp b/irr/src/CXMeshFileLoader.cpp
index 69ab2d0ca..59455a3cf 100644
--- a/irr/src/CXMeshFileLoader.cpp
+++ b/irr/src/CXMeshFileLoader.cpp
@@ -514,6 +514,8 @@ bool CXMeshFileLoader::parseDataObjectFrame(SkinnedMesh::SJoint *Parent)
 		if (n.has_value()) {
 			JointID = *n;
 			joint = AnimatedMesh->getAllJoints()[JointID];
+			if (Parent)
+				joint->ParentJointID = Parent->JointID;
 		}
 	}
 
diff --git a/irr/src/SkinnedMesh.cpp b/irr/src/SkinnedMesh.cpp
index e9dcc40f5..1237c3b6d 100644
--- a/irr/src/SkinnedMesh.cpp
+++ b/irr/src/SkinnedMesh.cpp
@@ -265,7 +265,7 @@ void SkinnedMesh::resetAnimation()
 
 //! Turns the given array of local matrices into an array of global matrices
 //! by multiplying with respective parent matrices.
-void SkinnedMesh::calculateGlobalMatrices(std::vector<core::matrix4> &matrices)
+void SkinnedMesh::calculateGlobalMatrices(std::vector<core::matrix4> &matrices) const
 {
 	// Note that the joints are topologically sorted.
 	for (u16 i = 0; i < AllJoints.size(); ++i) {
@@ -409,40 +409,45 @@ void SkinnedMesh::recalculateBaseBoundingBoxes() {
 	calculateBufferBoundingBoxes();
 }
 
-// TODO this can be removed: Our API guarantees topo sorting if we prevent mutation
 void SkinnedMesh::topoSortJoints()
 {
 	size_t n = AllJoints.size();
 
-	std::vector<u16> permutation; // new id -> old id
+	std::vector<u16> new_to_old_id; // new id -> old id
 
-	std::vector<std::vector<u16>> children(AllJoints.size());
+	std::vector<std::vector<u16>> children(n);
 	for (u16 i = 0; i < n; ++i) {
 		if (auto parentId = AllJoints[i]->ParentJointID)
 			children[*parentId].push_back(i);
 		else
-		 	permutation.push_back(i);
+		 	new_to_old_id.push_back(i);
 	}
 
 	// Levelorder
 	for (u16 i = 0; i < n; ++i) {
-		permutation.insert(permutation.end(),
-				children[i].begin(), children[i].end());
+		new_to_old_id.insert(new_to_old_id.end(),
+				children[new_to_old_id[i]].begin(),
+				children[new_to_old_id[i]].end());
 	}
 
 	// old id -> new id
-	std::vector<u16> inverse_permutation(n);
+	std::vector<u16> old_to_new_id(n);
 	for (u16 i = 0; i < n; ++i)
-		inverse_permutation[permutation[i]] = i;
+		old_to_new_id[new_to_old_id[i]] = i;
 
 	std::vector<SJoint *> joints(n);
 	for (u16 i = 0; i < n; ++i) {
-		joints[i] = AllJoints[permutation[i]];
+		joints[i] = AllJoints[new_to_old_id[i]];
 		joints[i]->JointID = i;
 		if (auto parentId = joints[i]->ParentJointID)
-			joints[i]->ParentJointID = inverse_permutation[*parentId];
+			joints[i]->ParentJointID = old_to_new_id[*parentId];
+	}
+	AllJoints = std::move(joints);
+
+	for (u16 i = 0; i < n; ++i) {
+		if (auto pjid = AllJoints[i]->ParentJointID)
+			assert(*pjid < i);
 	}
-	AllJoints = joints;
 }
 
 //! called by loader after populating with mesh and bone data
@@ -469,7 +474,6 @@ SkinnedMesh *SkinnedMeshBuilder::finalize()
 	}
 	calculateGlobalMatrices(matrices);
 
-	
 	for (size_t i = 0; i < AllJoints.size(); ++i) {
 		auto *joint = AllJoints[i];
 		if (!joint->GlobalInversedMatrix) {