diff --git a/awacs/__init__.py b/awacs/__init__.py
index 2f9e687c..f0dd93df 100644
--- a/awacs/__init__.py
+++ b/awacs/__init__.py
@@ -111,7 +111,7 @@ def JSONrepr(self) -> dict:
         self.validate()
         return self.resource
 
-    def to_json(self, indent: int = 4, sort_keys: bool = True) -> str:
+    def to_json(self, indent: Optional[int] = 4, sort_keys: bool = True) -> str:
         p = self.properties
         return json.dumps(p, cls=awsencode, indent=indent, sort_keys=sort_keys)
 
@@ -149,7 +149,7 @@ def getdata(self, data: Union[AWSObject, T]) -> Union[str, None, T]:
         else:
             return data
 
-    def to_json(self, indent: int = 4, sort_keys: bool = True) -> str:
+    def to_json(self, indent: Optional[int] = 4, sort_keys: bool = True) -> str:
         p = self
         return json.dumps(p, cls=awsencode, indent=indent, sort_keys=sort_keys)
 
diff --git a/tests/test_base.py b/tests/test_base.py
index dc44a499..8e881edf 100644
--- a/tests/test_base.py
+++ b/tests/test_base.py
@@ -50,6 +50,22 @@ def test_invalid_property(self):
             "'statement'",
         )
 
+    def test_to_json(self):
+        p = PolicyDocument(Version="2012-10-17", Statement=[])
+
+        self.assertEqual(
+            p.to_json(),
+            '{\n    "Statement": [],\n    "Version": "2012-10-17"\n}',
+        )
+
+    def test_to_json_indent_non(self):
+        p = PolicyDocument(Version="2012-10-17", Statement=[])
+
+        self.assertEqual(
+            p.to_json(indent=None),
+            '{"Statement": [], "Version": "2012-10-17"}',
+        )
+
 
 class TestAWSProperty(unittest.TestCase):
     def test_prop_value_type_mismatch_expect_list(self):