diff --git a/src/ifcpatch/ifcpatch/recipes/Fix12DToRevitTINs.py b/src/ifcpatch/ifcpatch/recipes/Fix12DToRevitTINs.py
index 63e54e5261..f4b88c8b9b 100644
--- a/src/ifcpatch/ifcpatch/recipes/Fix12DToRevitTINs.py
+++ b/src/ifcpatch/ifcpatch/recipes/Fix12DToRevitTINs.py
@@ -15,10 +15,10 @@ class Patcher:
         # The solution will merge vertices closer than 10mm to prevent dense
         # portions of the TIN at a minor sacrifice of surveying accuracy. It
         # will also triangulate all meshes to prevent non-coplanar surfaces, and
-        # delete any obtuse triangles where one of their angles is less than 0.3
-        # degrees. Therefore the result will contain some minor "holes" in the
-        # TIN, but these holes will only be in dense triangles that Revit can't
-        # handle anyway and won't affect most coordination tasks.
+        # delete any obtuse triangles where one of their XY angles is less than
+        # 0.3 degrees. Therefore the result will contain some minor "holes" in
+        # the TIN, but these holes will only be in dense triangles that Revit
+        # can't handle anyway and won't affect most coordination tasks.
         #
         # This patch is designed to only work on 12D IFC exports. It also
         # requires you to run it using Blender, as the geometric modification
@@ -47,7 +47,7 @@ class Patcher:
             bmesh.ops.triangulate(bm, faces=bm.faces[:], quad_method='BEAUTY', ngon_method='BEAUTY')
             bm.faces.ensure_lookup_table()
             for polygon in bm.faces:
-                v1, v2, v3 = [v.co for v in polygon.verts]
+                v1, v2, v3 = [v.co.to_2d() for v in polygon.verts]
                 d1 = degrees((v2-v1).angle(v3-v1))
                 d2 = degrees((v3-v2).angle(v1-v2))
                 d3 = degrees((v1-v3).angle(v2-v3))