diff --git a/src/ifcopenshell-python/ifcopenshell/util/data.py b/src/ifcopenshell-python/ifcopenshell/util/data.py
index 3c1e2c1669..a66ea80252 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/data.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/data.py
@@ -78,7 +78,9 @@ class Clipping:
         direction = ifc_file.createIfcDirection(self.normal)
 
         normal = np.array(self.normal)
-        if np.allclose(normal, np.array([0.0, 0.0, 1.0]), atol=1e-2):
+        if np.allclose(normal, np.array([0.0, 0.0, 1.0]), atol=1e-2) or np.allclose(
+            normal, np.array([0.0, 0.0, -1.0]), atol=1e-2
+        ):
             arbitrary_vector = np.array([0.0, 1.0, 0.0])
         else:
             arbitrary_vector = np.array([0.0, 0.0, 1.0])