diff --git a/modules/gridmap/grid_map.cpp b/modules/gridmap/grid_map.cpp
index ff52a67dbc7..f5fcc2aa8a4 100644
--- a/modules/gridmap/grid_map.cpp
+++ b/modules/gridmap/grid_map.cpp
@@ -354,10 +354,7 @@ void GridMap::set_cell_item(const Vector3i &p_position, int p_item, int p_rot) {
 	key.y = p_position.y;
 	key.z = p_position.z;
 
-	OctantKey ok;
-	ok.x = p_position.x / octant_size;
-	ok.y = p_position.y / octant_size;
-	ok.z = p_position.z / octant_size;
+	const OctantKey ok = get_octant_key_from_cell_coords(p_position);
 
 	if (p_item < 0) {
 		//erase
@@ -521,6 +518,32 @@ int GridMap::get_orthogonal_index_from_basis(const Basis &p_basis) const {
 	return 0;
 }
 
+GridMap::OctantKey GridMap::get_octant_key_from_index_key(const IndexKey &p_index_key) const {
+	const int x = p_index_key.x > 0 ? p_index_key.x / octant_size : (p_index_key.x - (octant_size - 1)) / octant_size;
+	const int y = p_index_key.y > 0 ? p_index_key.y / octant_size : (p_index_key.y - (octant_size - 1)) / octant_size;
+	const int z = p_index_key.z > 0 ? p_index_key.z / octant_size : (p_index_key.z - (octant_size - 1)) / octant_size;
+
+	OctantKey ok;
+	ok.key = 0;
+	ok.x = x;
+	ok.y = y;
+	ok.z = z;
+	return ok;
+}
+
+GridMap::OctantKey GridMap::get_octant_key_from_cell_coords(const Vector3i &p_cell_coords) const {
+	const int x = p_cell_coords.x > 0 ? p_cell_coords.x / octant_size : (p_cell_coords.x - (octant_size - 1)) / octant_size;
+	const int y = p_cell_coords.y > 0 ? p_cell_coords.y / octant_size : (p_cell_coords.y - (octant_size - 1)) / octant_size;
+	const int z = p_cell_coords.z > 0 ? p_cell_coords.z / octant_size : (p_cell_coords.z - (octant_size - 1)) / octant_size;
+
+	OctantKey ok;
+	ok.key = 0;
+	ok.x = x;
+	ok.y = y;
+	ok.z = z;
+	return ok;
+}
+
 Vector3i GridMap::local_to_map(const Vector3 &p_world_position) const {
 	Vector3 map_position = (p_world_position / cell_size).floor();
 	return Vector3i(map_position);
@@ -1320,10 +1343,7 @@ void GridMap::make_baked_meshes(bool p_gen_lightmap_uv, float p_lightmap_uv_texe
 		xform.set_origin(cellpos * cell_size + ofs);
 		xform.basis.scale(Vector3(cell_scale, cell_scale, cell_scale));
 
-		OctantKey ok;
-		ok.x = key.x / octant_size;
-		ok.y = key.y / octant_size;
-		ok.z = key.z / octant_size;
+		const OctantKey ok = get_octant_key_from_index_key(key);
 
 		if (!surface_map.has(ok)) {
 			surface_map[ok] = HashMap<Ref<Material>, Ref<SurfaceTool>>();
diff --git a/modules/gridmap/grid_map.h b/modules/gridmap/grid_map.h
index b9db20fec2e..fdad87a41a1 100644
--- a/modules/gridmap/grid_map.h
+++ b/modules/gridmap/grid_map.h
@@ -152,6 +152,9 @@ class GridMap : public Node3D {
 		OctantKey() {}
 	};
 
+	OctantKey get_octant_key_from_index_key(const IndexKey &p_index_key) const;
+	OctantKey get_octant_key_from_cell_coords(const Vector3i &p_cell_coords) const;
+
 #ifndef PHYSICS_3D_DISABLED
 	uint32_t collision_layer = 1;
 	uint32_t collision_mask = 1;