diff --git a/src/c3nav/mapdata/render/data.py b/src/c3nav/mapdata/render/data.py
index 8cbb629f..58519f5c 100644
--- a/src/c3nav/mapdata/render/data.py
+++ b/src/c3nav/mapdata/render/data.py
@@ -518,7 +518,7 @@ class LevelGeometries:
         # lower faces
         new_faces.append(np.dstack((self.vertices[np.flip(geom_faces, axis=1)], bottom[geom_faces])))
 
-        return (np.vstack(new_faces), )
+        return tuple((np.vstack(new_faces), ))
 
     def build_mesh(self, interpolator=None):
         rings = tuple(chain(*(get_rings(geom) for geom in self.get_geometries())))
@@ -566,7 +566,6 @@ class LevelGeometries:
         self.optional_base.build_polyhedron(self._create_polyhedron, bottom=0, top=1)
 
         # unset heightareas, they are no loinger needed
-        self.vertex_altitudes = None
         self.heightareas = None
         self.vertices = None
         self.faces = None
diff --git a/src/c3nav/mapdata/render/engines/base3d.py b/src/c3nav/mapdata/render/engines/base3d.py
index 86fcc7e6..df48158e 100644
--- a/src/c3nav/mapdata/render/engines/base3d.py
+++ b/src/c3nav/mapdata/render/engines/base3d.py
@@ -7,6 +7,7 @@ from c3nav.mapdata.render.data import HybridGeometry
 from c3nav.mapdata.render.engines.base import FillAttribs, RenderEngine, StrokeAttribs
 
 
+# noinspection PyAbstractClass
 class Base3DEngine(RenderEngine):
     is_3d = True
 
@@ -22,7 +23,8 @@ class Base3DEngine(RenderEngine):
         if fill is not None:
             self.vertices.append(self._place_geometry(geometry))
 
-    def _append_to_vertices(self, vertices, append=None):
+    @staticmethod
+    def _append_to_vertices(vertices, append=None):
         if append is not None:
             append = np.array(append, dtype=np.float32).flatten()
             vertices = np.dstack((
diff --git a/src/c3nav/mapdata/utils/mesh.py b/src/c3nav/mapdata/utils/mesh.py
index 72ecef9e..27f253a8 100644
--- a/src/c3nav/mapdata/utils/mesh.py
+++ b/src/c3nav/mapdata/utils/mesh.py
@@ -10,6 +10,7 @@ from shapely.geometry import MultiPolygon, Polygon
 
 @lru_cache()
 def get_face_indizes(start, length):
+    # noinspection PyTypeChecker
     indices = np.tile(np.arange(start, start + length).reshape((-1, 1)), 2).flatten()[1:-1].reshape((length - 1, 2))
     return np.vstack((indices, (indices[-1][-1], indices[0][0])))
 
@@ -28,6 +29,7 @@ def triangulate_rings(rings, holes=None):
         indices = tuple(vertices_lookup[vertex] for vertex in ring[:-1])
         segments.update(zip(indices, indices[1:]+indices[:1]))
 
+    # noinspection PyArgumentList
     info = triangle.MeshInfo()
     info.set_points(np.array(vertices).tolist())
     info.set_facets(segments)
@@ -50,6 +52,7 @@ def _triangulate_polygon(polygon: Polygon, keep_holes=False):
         segments.append(get_face_indizes(offset, len(new_vertices)))
         offset += len(new_vertices)
 
+    # noinspection PyArgumentList
     info = triangle.MeshInfo()
     info.set_points(np.vstack(vertices))
     info.set_facets(np.vstack(segments).tolist())