diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index e964156..8fc05df 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -19,12 +19,12 @@
 
       strategy:
         matrix:
-          platform: ["ubuntu-latest"]
+          platform: ["ubuntu-20.04"]
           python-version: ["3.6", "3.7", "3.8"]
 
       steps:
-        - uses: "actions/checkout@v2"
-        - uses: "actions/setup-python@v2"
+        - uses: "actions/checkout@v3"
+        - uses: "actions/setup-python@v4"
           with:
             python-version: "${{ matrix.python-version }}"
         - name: "Install dependencies"
@@ -44,8 +44,8 @@
       runs-on: "ubuntu-latest"
 
       steps:
-        - uses: "actions/checkout@v2"
-        - uses: "actions/setup-python@v2"
+        - uses: "actions/checkout@v3"
+        - uses: "actions/setup-python@v4"
           with:
             python-version: "3.8"
 
@@ -67,8 +67,8 @@
       runs-on: "${{ matrix.os }}"
 
       steps:
-        - uses: "actions/checkout@v2"
-        - uses: "actions/setup-python@v2"
+        - uses: "actions/checkout@v3"
+        - uses: "actions/setup-python@v4"
           with:
             python-version: "3.8"
         - name: "Install in dev mode"
diff --git a/rest_framework_yaml/encoders.py b/rest_framework_yaml/encoders.py
index e9e0c5a..3646d59 100644
--- a/rest_framework_yaml/encoders.py
+++ b/rest_framework_yaml/encoders.py
@@ -48,7 +48,10 @@ def represent_mapping(self, tag, mapping, flow_style=None):
         if hasattr(mapping, "items"):
             mapping = list(mapping.items())
             if not isinstance(mapping, OrderedDict):
-                mapping.sort()
+                try:
+                    mapping.sort()
+                except TypeError:
+                    pass
         for item_key, item_value in mapping:
             item_value = self._fix_value_before_representation(item_value)
             node_key = self.represent_data(item_key)
diff --git a/tests/test_renderers.py b/tests/test_renderers.py
index 4d3c402..2a29e20 100644
--- a/tests/test_renderers.py
+++ b/tests/test_renderers.py
@@ -103,3 +103,16 @@ def test_proper_encoding(self):
         renderer = YAMLRenderer()
         content = renderer.render(obj, "application/yaml")
         self.assertEqual(content.strip(), _yaml_repr.encode("utf-8"))
+
+    def test_render_none_type(self):
+        """
+        Test YAML rendering with None type
+        """
+        _yaml_repr = "foo:\n- bar\n- baz\nnull:\n- null\n"
+
+        obj = {"foo": ["bar", "baz"], None: [None]}
+
+        renderer = YAMLRenderer()
+        content = renderer.render(obj, "application/yaml")
+
+        self.assertEqual(_yaml_repr, content.decode("utf-8"))