diff --git a/tests/conftest.py b/tests/conftest.py
index cee06ba..4075a82 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -15,21 +15,26 @@ def mock_subtransaction(request):
 
 @pytest.fixture
 def mock_original_transaction(request):
-	subs = ()
-	try:
-		if request.param:
+	subs = tuple()
+	memo = 'memo'
+	category = Category(id='cid1', name='cname')
+	flag_color = 'red'
+	if hasattr(request, 'param'):
+		if request.param == 'subtransactions':
 			st = OriginalSubTransaction(memo='memo1', amount=500,
 								   category=Category(name='cname', id='cid'),
 								   payee=Payee(name='pname'))
 			subs = (st, st)
-	except AttributeError as e:
-		pass
+		if request.param == 'optional_none':
+			memo = None
+			category = None
+			flag_color = None
 	return OriginalTransaction(id='id',
-							   memo='memo',
-							   category=Category(id='cid1', name='cname'),
+							   memo=memo,
+							   category=category,
 							   payee=Payee(id='pid', name='pname'),
 							   subtransactions=subs,
-							   flag_color='red',
+							   flag_color=flag_color,
 							   amount=1000,
 							   import_payee_name='ipn',
 							   import_payee_name_original='ipno',
diff --git a/tests/test_modifiedtransaction.py b/tests/test_modifiedtransaction.py
index ccc4527..dbd309c 100644
--- a/tests/test_modifiedtransaction.py
+++ b/tests/test_modifiedtransaction.py
@@ -26,6 +26,23 @@ def test_is_changed_true(test_attribute, test_input, mock_original_transaction):
 	assert r is True
 
 
+@pytest.mark.parametrize('mock_original_transaction', ['optional_none'], indirect=True)
+@pytest.mark.parametrize('test_attribute, test_input', [
+	('memo', 'memox'),
+	('category', Category(id='c_id1', name='c_name1')),
+])
+def test_is_changed_true_none_values_in_original(test_attribute, test_input, mock_original_transaction):
+	# Arrange
+	mock_modifier = TransactionModifier.from_original_transaction(mock_original_transaction)
+	mock_modifier.__setattr__(test_attribute, test_input)
+	modified = ModifiedTransaction(original_transaction=mock_original_transaction, transaction_modifier=mock_modifier)
+
+	# Act
+	r = modified.is_changed()
+	assert r is True
+
+
+@pytest.mark.parametrize('mock_original_transaction', [None, 'optional_none'], indirect=True)
 def test_changed_false(mock_original_transaction):
 	# Arrange
 	mock_modifier = TransactionModifier.from_original_transaction(mock_original_transaction)
@@ -36,7 +53,7 @@ def test_changed_false(mock_original_transaction):
 	assert r is False
 
 
-@pytest.mark.parametrize('mock_original_transaction', [True], indirect=True)
+@pytest.mark.parametrize('mock_original_transaction', ['subtransactions'], indirect=True)
 def test_invalid_subtransactions(mock_original_transaction, mock_subtransaction):
 	# Arrange
 	mock_modifier = TransactionModifier.from_original_transaction(mock_original_transaction)
diff --git a/ynabtransactionadjuster/models/modifiedtransaction.py b/ynabtransactionadjuster/models/modifiedtransaction.py
index d4a731f..f0b2d6e 100644
--- a/ynabtransactionadjuster/models/modifiedtransaction.py
+++ b/ynabtransactionadjuster/models/modifiedtransaction.py
@@ -40,35 +40,31 @@ def as_dict(self) -> dict:
 
 	def changed_attributes(self) -> dict:
 		"""Returns a dictionary representation of the modified values and the original transaction"""
-		changed_attributes = {}
-		if self.transaction_modifier.payee != self.original_transaction.payee:
-			changed_attributes['payee'] = dict(original=self.original_transaction.payee,
-											   changed=self.transaction_modifier.payee)
+		changed_attributes = dict()
+
+		for a in ('payee', 'category', 'flag_color', 'memo', 'approved', 'cleared'):
+			if self._attribute_changed(a):
+				changed_attributes[a] = self._create_changed_dict(a)
+
 		if (self.transaction_modifier.transaction_date.isocalendar() !=
 				self.original_transaction.transaction_date.isocalendar()):
-			changed_attributes['transaction_date'] = dict(original=self.original_transaction.transaction_date,
-														  changed=self.transaction_modifier.transaction_date)
-		if (self.transaction_modifier.category and
-				self.transaction_modifier.category.id != self.original_transaction.category.id):
-			changed_attributes['category'] = dict(original=self.original_transaction.category,
-												  changed=self.transaction_modifier.category)
-		if self.transaction_modifier.memo != self.original_transaction.memo:
-			changed_attributes['memo'] = dict(original=self.original_transaction.memo,
-											  changed=self.transaction_modifier.memo)
-		if self.transaction_modifier.flag_color != self.original_transaction.flag_color:
-			changed_attributes['flag_color'] = dict(original=self.original_transaction.flag_color,
-													changed=self.transaction_modifier.flag_color)
+			changed_attributes['transaction_date'] = self._create_changed_dict('transaction_date')
+
 		if len(self.transaction_modifier.subtransactions) > 0:
-			changed_attributes['subtransactions'] = dict(original=[],
-														 changed=self.transaction_modifier.subtransactions)
-		if self.transaction_modifier.approved != self.original_transaction.approved:
-			changed_attributes['approved'] = dict(original=self.original_transaction.approved,
-												  changed=self.transaction_modifier.approved)
-		if self.transaction_modifier.cleared != self.original_transaction.cleared:
-			changed_attributes['cleared'] = dict(original=self.original_transaction.cleared,
-												 changed=self.transaction_modifier.cleared)
+			changed_attributes['subtransactions'] = self._create_changed_dict('subtransactions')
+
 		return changed_attributes
 
+	def _attribute_changed(self, attribute: str) -> bool:
+		o = self.original_transaction.__getattribute__(attribute)
+		m = self.transaction_modifier.__getattribute__(attribute)
+		if o != m:
+			return True
+
+	def _create_changed_dict(self, attribute: str) -> dict:
+		return dict(original=self.original_transaction.__getattribute__(attribute),
+											  changed=self.transaction_modifier.__getattribute__(attribute))
+
 	@model_validator(mode='after')
 	def check_values(self):
 		if len(self.transaction_modifier.subtransactions) > 1: