diff --git a/src/ifcopenshell-python/ifcopenshell/util/unit.py b/src/ifcopenshell-python/ifcopenshell/util/unit.py
index a9b6e31c34..35f97ae3cd 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/unit.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/unit.py
@@ -566,8 +566,8 @@ def convert(value, from_prefix, from_unit, to_prefix, to_unit):
     return value
 
 
-def calculate_unit_scale(ifc_file, unit_type='LENGTHUNIT'):
-    """Returns a unit scale factor to convert to and from IFC project length units and SI meters
+def calculate_unit_scale(ifc_file, unit_type="LENGTHUNIT"):
+    """Returns a unit scale factor to convert to and from IFC project units and SI units.
 
     Example:
 
diff --git a/src/ifcopenshell-python/test/util/test_unit.py b/src/ifcopenshell-python/test/util/test_unit.py
index 4b978a6e82..52a6a93178 100644
--- a/src/ifcopenshell-python/test/util/test_unit.py
+++ b/src/ifcopenshell-python/test/util/test_unit.py
@@ -20,6 +20,7 @@ import pytest
 import test.bootstrap
 import ifcopenshell.api
 import ifcopenshell.util.unit as subject
+from math import pi
 
 
 class TestCalculateUnitScale(test.bootstrap.IFC4):
@@ -30,6 +31,11 @@ class TestCalculateUnitScale(test.bootstrap.IFC4):
         ifcopenshell.api.run("unit.assign_unit", self.file, units=[length])
         assert subject.calculate_unit_scale(self.file) == 0.3048 * 0.001
 
+        angle = ifcopenshell.api.run("unit.add_conversion_based_unit", self.file, name="degree")
+        angle.ConversionFactor.UnitComponent.Prefix = "MILLI"
+        ifcopenshell.api.run("unit.assign_unit", self.file, units=[angle])
+        assert subject.calculate_unit_scale(self.file, "PLANEANGLEUNIT") == pi / 180 * 0.001
+
 
 class TestFormatLength(test.bootstrap.IFC4):
     def test_run(self):