diff --git a/CHANGELOG.md b/CHANGELOG.md
index b72777e30..3924cb1b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixes
 
+- Endpoint tags are now sanitized during parsing to fix an issue where `My Tag` and `MyTag` are seen as two different tags but are then later unified, causing errors when creating directories. Thanks @p1-ra! (#328)
 - Parser will softly ignore value error during schema responses' status code convertion from string to integer (not a number). Errors will be reported to the end user and parsing will continue to proceed (#327).
 - The generated `from_dict` and `to_dict` methods of models will now properly handle `nullable` and `not required` properties that are themselves generated models (#315). Thanks @forest-benchling!
 - Fix deserialization of `None` and `Unset` properties for all types by unifying the checks (#334). Thanks @forest-benchling!
diff --git a/openapi_python_client/__init__.py b/openapi_python_client/__init__.py
index 74de04520..8c97d45e9 100644
--- a/openapi_python_client/__init__.py
+++ b/openapi_python_client/__init__.py
@@ -235,7 +235,6 @@ def _build_api(self) -> None:
 
         endpoint_template = self.env.get_template("endpoint_module.py.jinja")
         for tag, collection in self.openapi.endpoint_collections_by_tag.items():
-            tag = utils.snake_case(tag)
             tag_dir = api_dir / tag
             tag_dir.mkdir()
             (tag_dir / "__init__.py").touch()
diff --git a/openapi_python_client/parser/openapi.py b/openapi_python_client/parser/openapi.py
index 8aa97422d..65acceb24 100644
--- a/openapi_python_client/parser/openapi.py
+++ b/openapi_python_client/parser/openapi.py
@@ -48,7 +48,7 @@ def from_data(
                 operation: Optional[oai.Operation] = getattr(path_data, method)
                 if operation is None:
                     continue
-                tag = (operation.tags or ["default"])[0]
+                tag = utils.snake_case((operation.tags or ["default"])[0])
                 collection = endpoints_by_tag.setdefault(tag, EndpointCollection(tag=tag))
                 endpoint, schemas = Endpoint.from_data(
                     data=operation, path=path, method=method, tag=tag, schemas=schemas
diff --git a/tests/test_parser/test_openapi.py b/tests/test_parser/test_openapi.py
index cf1c9ba14..1336c6c39 100644
--- a/tests/test_parser/test_openapi.py
+++ b/tests/test_parser/test_openapi.py
@@ -829,3 +829,51 @@ def test_from_data_errors(self, mocker):
         assert result["default"].parse_errors[1].data == "3"
         assert result["tag_2"].parse_errors[0].data == "2"
         assert result_schemas == schemas_3
+
+    def test_from_data_tags_snake_case_sanitizer(self, mocker):
+        from openapi_python_client.parser.openapi import Endpoint, EndpointCollection
+
+        path_1_put = oai.Operation.construct()
+        path_1_post = oai.Operation.construct(tags=["AMF Subscription Info (Document)", "tag_3"])
+        path_2_get = oai.Operation.construct()
+        data = {
+            "path_1": oai.PathItem.construct(post=path_1_post, put=path_1_put),
+            "path_2": oai.PathItem.construct(get=path_2_get),
+        }
+        endpoint_1 = mocker.MagicMock(autospec=Endpoint, tag="default", relative_imports={"1", "2"})
+        endpoint_2 = mocker.MagicMock(autospec=Endpoint, tag="AMFSubscriptionInfo (Document)", relative_imports={"2"})
+        endpoint_3 = mocker.MagicMock(autospec=Endpoint, tag="default", relative_imports={"2", "3"})
+        schemas_1 = mocker.MagicMock()
+        schemas_2 = mocker.MagicMock()
+        schemas_3 = mocker.MagicMock()
+        endpoint_from_data = mocker.patch.object(
+            Endpoint,
+            "from_data",
+            side_effect=[(endpoint_1, schemas_1), (endpoint_2, schemas_2), (endpoint_3, schemas_3)],
+        )
+        schemas = mocker.MagicMock()
+
+        result = EndpointCollection.from_data(data=data, schemas=schemas)
+
+        endpoint_from_data.assert_has_calls(
+            [
+                mocker.call(data=path_1_put, path="path_1", method="put", tag="default", schemas=schemas),
+                mocker.call(
+                    data=path_1_post,
+                    path="path_1",
+                    method="post",
+                    tag="amf_subscription_info_document",
+                    schemas=schemas_1,
+                ),
+                mocker.call(data=path_2_get, path="path_2", method="get", tag="default", schemas=schemas_2),
+            ],
+        )
+        assert result == (
+            {
+                "default": EndpointCollection("default", endpoints=[endpoint_1, endpoint_3]),
+                "amf_subscription_info_document": EndpointCollection(
+                    "amf_subscription_info_document", endpoints=[endpoint_2]
+                ),
+            },
+            schemas_3,
+        )