diff --git a/src/ifcopenshell-python/test/fixtures/validate/fail-unit-derived-nil.ifc b/src/ifcopenshell-python/test/fixtures/validate/fail-unit-derived-nil.ifc
new file mode 100644
index 0000000000..7cadcf8488
--- /dev/null
+++ b/src/ifcopenshell-python/test/fixtures/validate/fail-unit-derived-nil.ifc
@@ -0,0 +1,10 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [CoordinationView]'),'2;1');
+FILE_NAME('','2022-10-02T14:16:07',(),(),'IfcOpenShell 0.7.0','IfcOpenShell 0.7.0','');
+FILE_SCHEMA(('IFC4'));
+ENDSEC;
+DATA;
+#1=IFCSIUNIT($,.LENGTHUNIT.,$,.METRE.);
+ENDSEC;
+END-ISO-10303-21;
diff --git a/src/ifcopenshell-python/test/fixtures/validate/fail-unit-nil-derived.ifc b/src/ifcopenshell-python/test/fixtures/validate/fail-unit-nil-derived.ifc
new file mode 100644
index 0000000000..844cbf5583
--- /dev/null
+++ b/src/ifcopenshell-python/test/fixtures/validate/fail-unit-nil-derived.ifc
@@ -0,0 +1,10 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [CoordinationView]'),'2;1');
+FILE_NAME('','2022-10-02T14:16:07',(),(),'IfcOpenShell 0.7.0','IfcOpenShell 0.7.0','');
+FILE_SCHEMA(('IFC4'));
+ENDSEC;
+DATA;
+#1=IFCSIUNIT(*,.LENGTHUNIT.,*,.METRE.);
+ENDSEC;
+END-ISO-10303-21;
diff --git a/src/ifcopenshell-python/test/fixtures/validate/pass-unit-derived-ok.ifc b/src/ifcopenshell-python/test/fixtures/validate/pass-unit-derived-ok.ifc
new file mode 100644
index 0000000000..2479561a8d
--- /dev/null
+++ b/src/ifcopenshell-python/test/fixtures/validate/pass-unit-derived-ok.ifc
@@ -0,0 +1,10 @@
+ISO-10303-21;
+HEADER;
+FILE_DESCRIPTION(('ViewDefinition [CoordinationView]'),'2;1');
+FILE_NAME('','2022-10-02T14:16:07',(),(),'IfcOpenShell 0.7.0','IfcOpenShell 0.7.0','');
+FILE_SCHEMA(('IFC4'));
+ENDSEC;
+DATA;
+#1=IFCSIUNIT(*,.LENGTHUNIT.,$,.METRE.);
+ENDSEC;
+END-ISO-10303-21;
diff --git a/src/ifcopenshell-python/test/validate.py b/src/ifcopenshell-python/test/validate.py
index 5ad4a83f45..41dd751cea 100644
--- a/src/ifcopenshell-python/test/validate.py
+++ b/src/ifcopenshell-python/test/validate.py
@@ -31,11 +31,14 @@ import ifcopenshell.validate
 def test_file(file):
     logger = ifcopenshell.validate.json_logger()
     ifcopenshell.validate.validate(file, logger)
-    if file.startswith("fail-"):
+    print()
+    for x in logger.statements:
+        print(x['message'])
+    if os.path.basename(file).startswith("fail-"):
         assert len(logger.statements) > 0
-    if file.startswith("pass-"):
+    if os.path.basename(file).startswith("pass-"):
         assert len(logger.statements) == 0
 
 
 if __name__ == "__main__":
-    pytest.main(["-sx", __file__])
+    pytest.main(["-svx", __file__])