diff --git a/src/core_codemods/harden_pyyaml.py b/src/core_codemods/harden_pyyaml.py
index 00c7f2a68..84a450cd7 100644
--- a/src/core_codemods/harden_pyyaml.py
+++ b/src/core_codemods/harden_pyyaml.py
@@ -73,6 +73,7 @@ def on_result_found(
         original_node: Union[cst.Call, cst.ClassDef],
         updated_node: Union[cst.Call, cst.ClassDef],
     ):
+        # TODO: provide different change description for each case.
         match original_node:
             case cst.Call():
                 maybe_name = self.get_aliased_prefix_name(
@@ -102,7 +103,16 @@ def _update_bases(self, original_node: cst.ClassDef) -> list[cst.Arg]:
             | matchers.Name(value="BaseLoader")
             | matchers.Name(value="FullLoader")
         )
+        base_names = [
+            f"yaml.{klas}"
+            for klas in ("UnsafeLoader", "Loader", "BaseLoader", "FullLoader")
+        ]
         for base_arg in original_node.bases:
+            base_name = self.find_base_name(base_arg.value)
+            if base_name not in base_names:
+                new.append(base_arg)
+                continue
+
             if matchers.matches(base_arg.value, unsafe_name_matchers):
                 self.add_needed_import(self._module_name, "SafeLoader")
                 self.remove_unused_import(base_arg.value)
diff --git a/tests/codemods/test_harden_pyyaml.py b/tests/codemods/test_harden_pyyaml.py
index da0a0bb6d..1e30f2827 100644
--- a/tests/codemods/test_harden_pyyaml.py
+++ b/tests/codemods/test_harden_pyyaml.py
@@ -164,18 +164,38 @@ def test_multiple_bases(self, tmpdir):
         input_code = """\
         from abc import ABC
         import yaml as yam
+        from whatever import Loader
 
-        class MyCustomLoader(ABC, yam.UnsafeLoader):
+        class MyCustomLoader(ABC, yam.UnsafeLoader, Loader):
             def __init__(self, *args, **kwargs):
                 super(MyCustomLoader, self).__init__(*args, **kwargs)
         """
         expected = """\
         from abc import ABC
         import yaml as yam
+        from whatever import Loader
 
-        class MyCustomLoader(ABC, yam.SafeLoader):
+        class MyCustomLoader(ABC, yam.SafeLoader, Loader):
             def __init__(self, *args, **kwargs):
                 super(MyCustomLoader, self).__init__(*args, **kwargs)
         """
         self.run_and_assert(tmpdir, input_code, expected)
         assert len(self.file_context.codemod_changes) == 1
+
+    def test_different_yaml(self, tmpdir):
+        input_code = """\
+        from yaml import UnsafeLoader
+        import whatever as yaml
+
+        class MyLoader(UnsafeLoader, yaml.Loader):
+            ...
+        """
+        expected = """\
+        from yaml import SafeLoader
+        import whatever as yaml
+
+        class MyLoader(SafeLoader, yaml.Loader):
+            ...
+        """
+        self.run_and_assert(tmpdir, input_code, expected)
+        assert len(self.file_context.codemod_changes) == 1