diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b2bd338ee7..ec2d62b411 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -74,6 +74,9 @@ jobs:
 
       - name: Build ifcopenshell
         run: |
+          echo $Python3_ROOT_DIR
+          echo ${{ env.pythonLocation }}
+          
           mkdir build && cd build
           cmake \
                -DCMAKE_C_COMPILER_LAUNCHER=ccache \
@@ -83,7 +86,9 @@ jobs:
                -DCMAKE_SYSTEM_PREFIX_PATH=/usr \
                -DOCC_INCLUDE_DIR=/usr/include/opencascade \
                -DOCC_LIBRARY_DIR=/usr/lib/x86_64-linux-gnu \
-               -DPython3_ROOT_DIR=$Python3_ROOT_DIR \
+               -DPYTHON_EXECUTABLE:FILEPATH=${{ env.pythonLocation }}/bin/python \
+               -DPYTHON_INCLUDE_DIR:PATH=${{ env.pythonLocation }}/include/python3.11 \
+               -DPYTHON_LIBRARY:FILEPATH=${{ env.pythonLocation }}/lib/libpython3.11.so \
                -DCOLLADA_SUPPORT=Off \
                "-DSCHEMA_VERSIONS=2x3;4;4x3_add2" \
                -DGLTF_SUPPORT=On \
diff --git a/src/ifcopenshell-python/ifcopenshell/util/unit.py b/src/ifcopenshell-python/ifcopenshell/util/unit.py
index 33ee3d9af3..cc20b88ac2 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/unit.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/unit.py
@@ -16,9 +16,12 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
-import ifcopenshell
-from math import pi
 from fractions import Fraction
+from math import pi
+from typing import Tuple, Iterable, Any
+
+import ifcopenshell
+import ifcopenshell.api
 
 prefixes = {
     "EXA": 1e18,
@@ -624,67 +627,75 @@ def format_length(
         return f"{rounded_val:.{decimal_places}f}"
 
 
-def get_base_type_name(
-        content_type: ifcopenshell.ifcopenshell_wrapper.named_type | ifcopenshell.ifcopenshell_wrapper.type_declaration) -> ifcopenshell.ifcopenshell_wrapper.type_declaration | None:
+def is_attr_type(
+        content_type: ifcopenshell.ifcopenshell_wrapper.named_type | ifcopenshell.ifcopenshell_wrapper.type_declaration,
+        ifc_unit_type_name: str) -> ifcopenshell.ifcopenshell_wrapper.type_declaration | None:
     cur_decl = content_type
     while hasattr(cur_decl, "declared_type") is True:
         cur_decl = cur_decl.declared_type()
         if hasattr(cur_decl, "name") is False:
             continue
-        if cur_decl.name() == "IfcLengthMeasure":
+        if cur_decl.name() == ifc_unit_type_name:
             return cur_decl
 
     if isinstance(cur_decl, ifcopenshell.ifcopenshell_wrapper.aggregation_type):
         res = cur_decl.type_of_element()
         cur_decl = res.declared_type()
-        if hasattr(cur_decl, "name") and cur_decl.name() == "IfcLengthMeasure":
+        if hasattr(cur_decl, "name") and cur_decl.name() == ifc_unit_type_name:
             return cur_decl
         while hasattr(cur_decl, "declared_type") is True:
             cur_decl = cur_decl.declared_type()
             if hasattr(cur_decl, "name") is False:
                 continue
-            if cur_decl.name() == "IfcLengthMeasure":
+            if cur_decl.name() == ifc_unit_type_name:
                 return cur_decl
 
     return None
 
 
+def iter_element_and_attributes_per_type(ifc_file: ifcopenshell.file, attr_type_name: str) -> Iterable[
+    Tuple[ifcopenshell.entity_instance, ifcopenshell.ifcopenshell_wrapper.attribute, Any, str]]:
+    schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name(ifc_file.schema)
+
+    for element in ifc_file:
+        entity = schema.declaration_by_name(element.is_a())
+        attrs = entity.all_attributes()
+        for i, (attr, val, is_derived) in enumerate(zip(attrs, list(element), entity.derived())):
+            if is_derived:
+                continue
+
+            # Get all methods and attributes of the element
+            attr_type = attr.type_of_attribute()
+            base_type = is_attr_type(attr_type, attr_type_name)
+            if base_type is None:
+                continue
+
+            if val is None:
+                continue
+
+            yield element, attr, val
+
+
 def convert_file_length_units(ifc_file: ifcopenshell.file, target_units: str) -> ifcopenshell.file:
     """Converts all units in an IFC file to the specified target units. Returns a new file."""
     prefix = "MILLI" if target_units == "MILLIMETERS" else None
 
-    file_patched = ifcopenshell.api.run("project.create_file", version=ifc_file.schema)
     # Copy all elements from the original file to the patched file
-    for el in ifc_file:
-        file_patched.add(el)
+    file_patched = ifcopenshell.file.from_string(ifc_file.wrapped_data.to_string())
 
     unit_assignment = ifcopenshell.util.unit.get_unit_assignment(file_patched)
 
     old_length = [u for u in unit_assignment.Units if getattr(u, "UnitType", None) == "LENGTHUNIT"][0]
     new_length = ifcopenshell.api.run("unit.add_si_unit", file_patched, unit_type="LENGTHUNIT", prefix=prefix)
 
-    schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name(ifc_file.schema)
     # Traverse all elements and their nested attributes in the file and convert them
-    for element in file_patched:
-        entity = schema.declaration_by_name(element.is_a())
-        attrs = entity.all_attributes()
-        for i, (attr, val, is_derived) in enumerate(zip(attrs, list(element), entity.derived())):
-            if is_derived:
-                continue
-            # Get all methods and attributes of the element
-            attr_type = attr.type_of_attribute()
-            base_type = get_base_type_name(attr_type)
-            if base_type is None:
-                continue
-            if val is None:
-                continue
-            if isinstance(val, tuple):
-                new_el = [ifcopenshell.util.unit.convert_unit(v, old_length, new_length) for v in val]
-                setattr(element, attr.name(), tuple(new_el))
-            else:
-                new_el = ifcopenshell.util.unit.convert_unit(val, old_length, new_length)
-                # set the new value
-                setattr(element, attr.name(), new_el)
+    for element, attr, val in iter_element_and_attributes_per_type(file_patched, "IfcLengthMeasure"):
+        if isinstance(val, tuple):
+            new_value = [ifcopenshell.util.unit.convert_unit(v, old_length, new_length) for v in val]
+            setattr(element, attr.name(), tuple(new_value))
+        else:
+            new_value = ifcopenshell.util.unit.convert_unit(val, old_length, new_length)
+            setattr(element, attr.name(), new_value)
 
     file_patched.remove(old_length)
     unit_assignment.Units = tuple([new_length, *unit_assignment.Units])
diff --git a/src/ifcopenshell-python/test/fixtures/units/beam-standard-case.ifc b/src/ifcopenshell-python/test/fixtures/units/beam-standard-case.ifc
new file mode 100644
index 0000000000..0f506b45a4
--- /dev/null
+++ b/src/ifcopenshell-python/test/fixtures/units/beam-standard-case.ifc
@@ -0,0 +1,426 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION((''),'2;1');
+FILE_NAME('','2019-03-20T15:56:44',(''),(''),'BuildingSmart IfcKit by Constructivity','IfcDoc 12.0.0.0','');
+FILE_SCHEMA(('IFC4x1'));
+ENDSEC;
+
+DATA;
+
+#1= IFCBEAMTYPE('0juf4qyggSstrxA20Qwnsj',$,'IPE220','Beam type',$,$,$,$,$,.BEAM.);
+
+#2= IFCRELDECLARES('3P3zL0KYv4C9D9h3OX$dey',$,$,$,#5,(#1,#6));
+
+#3= IFCRELASSOCIATESMATERIAL('0juf4qyggSstrxA20Q49sj',$,$,$,(#1),#7);
+#7= IFCMATERIALPROFILESET($,$,(#8),$);
+#8= IFCMATERIALPROFILE('IPE220',$,#9,#10,$,$);
+#9= IFCMATERIAL('S275J2',$,'Steel');
+#10= IFCISHAPEPROFILEDEF(.AREA.,'IPE220',$,110.,220.,5.9,9.2,12.,$,$);
+
+#4= IFCRELDEFINESBYTYPE('2aq$Crcs_xJvd69lbm2bMM',$,'beam typing',$,(#11,#12,#13,#14,#15,#16,#17,#18,#19),#1);
+
+#5= IFCPROJECT('32DJhIf6esIeAOIlD4Xw2m',#20,'Test model for beam cardinal points',$,$,$,$,(#21),#22);
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+ENDSEC;
+
+END-ISO-10303-21;
diff --git a/src/ifcopenshell-python/test/util/test_unit_conversion.py b/src/ifcopenshell-python/test/util/test_unit_conversion.py
new file mode 100644
index 0000000000..af84677647
--- /dev/null
+++ b/src/ifcopenshell-python/test/util/test_unit_conversion.py
@@ -0,0 +1,49 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2023 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+import pathlib
+
+import pytest
+
+import ifcopenshell.util.unit
+
+UNITS_FIXTURE_DIR = pathlib.Path(__file__).parent.parent / "fixtures" / "units"
+
+
+@pytest.mark.parametrize("ifc_file", UNITS_FIXTURE_DIR.glob("*.ifc"))
+def test_file_units_length_convert(ifc_file):
+    f = ifcopenshell.open(ifc_file)
+    project_unit = ifcopenshell.util.unit.get_project_unit(f, "LENGTHUNIT")
+    if project_unit.Prefix == "MILLI":
+        target_units = "METERS"
+        scale = 0.001
+    else:
+        target_units = "MILLIMETERS"
+        scale = 1000
+
+    new_f = ifcopenshell.util.unit.convert_file_length_units(f, target_units)
+
+    for element, attr, val in ifcopenshell.util.unit.iter_element_and_attributes_per_type(new_f, "IfcLengthMeasure"):
+        elem_id = element.id()
+        original_element = f.by_id(elem_id)
+        original_val = getattr(original_element, attr.name())
+        if isinstance(original_val, tuple):
+            # assert element is equal to original element times scale
+            assert val == tuple([v * scale for v in original_val])
+        else:
+            # assert element is equal to original element times scale
+            assert val == original_val * scale