diff --git a/apitools/base/py/base_api.py b/apitools/base/py/base_api.py
index 3a4071b..42412d8 100644
--- a/apitools/base/py/base_api.py
+++ b/apitools/base/py/base_api.py
@@ -100,6 +100,8 @@ class ApiMethodInfo(messages.Message):
       supports_download: (boolean) If True, this method supports
           downloading the request via the `alt=media` query
           parameter.
+      api_version_param: API version system parameter for this
+          method.
     """
 
     relative_path = messages.StringField(1)
@@ -115,6 +117,7 @@ class ApiMethodInfo(messages.Message):
     request_field = messages.StringField(11, default='')
     upload_config = messages.MessageField(ApiUploadInfo, 12)
     supports_download = messages.BooleanField(13, default=False)
+    api_version_param = messages.StringField(14)
 
 
 REQUEST_IS_BODY = '<request>'
@@ -634,6 +637,12 @@ def __SetBaseHeaders(self, http_request, client):
         http_request.headers['accept'] = 'application/json'
         http_request.headers['accept-encoding'] = 'gzip, deflate'
 
+    def __SetBaseSystemParams(self, http_request, method_config):
+      """Fill in the system parameters to always set for the method."""
+      if method_config.api_version_param:
+          http_request.headers['X-Goog-Api-Version'] = (
+              method_config.api_version_param)
+
     def __SetBody(self, http_request, method_config, request, upload):
         """Fill in the body on http_request."""
         if not method_config.request_field:
@@ -672,6 +681,7 @@ def PrepareHttpRequest(self, method_config, request, global_params=None,
         http_request = http_wrapper.Request(
             http_method=method_config.http_method)
         self.__SetBaseHeaders(http_request, self.__client)
+        self.__SetBaseSystemParams(http_request, method_config)
         self.__SetBody(http_request, method_config, request, upload)
 
         url_builder = _UrlBuilder(
diff --git a/apitools/base/py/base_api_test.py b/apitools/base/py/base_api_test.py
index 9de1de8..847b70a 100644
--- a/apitools/base/py/base_api_test.py
+++ b/apitools/base/py/base_api_test.py
@@ -220,10 +220,10 @@ def fakeMakeRequest(*unused_args, **unused_kwargs):
             with self.assertRaises(exceptions.HttpBadRequestError) as err:
                 service._RunMethod(method_config, request)
         http_error = err.exception
-        self.assertEquals('http://www.google.com', http_error.url)
-        self.assertEquals('{"field": "abc"}', http_error.content)
-        self.assertEquals(method_config, http_error.method_config)
-        self.assertEquals(request, http_error.request)
+        self.assertEqual('http://www.google.com', http_error.url)
+        self.assertEqual('{"field": "abc"}', http_error.content)
+        self.assertEqual(method_config, http_error.method_config)
+        self.assertEqual(request, http_error.request)
 
     def testQueryEncoding(self):
         method_config = base_api.ApiMethodInfo(
@@ -338,6 +338,16 @@ def testOverwritesTransferUrlBase(self):
         expected = 'http://custom.p.googleapis.com/path'
         self.assertEqual(observed, expected)
 
+    def testApiVersionSystemParameter(self):
+        method_config = base_api.ApiMethodInfo(
+            request_type_name='SimpleMessage', api_version_param='2024-01-01')
+        service = FakeService()
+        request = SimpleMessage()
+        http_request = service.PrepareHttpRequest(method_config, request)
+        self.assertIn('X-Goog-Api-Version', http_request.headers)
+        self.assertEqual(
+            '2024-01-01', http_request.headers['X-Goog-Api-Version'])
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/apitools/gen/service_registry.py b/apitools/gen/service_registry.py
index 6d396aa..434d124 100644
--- a/apitools/gen/service_registry.py
+++ b/apitools/gen/service_registry.py
@@ -407,6 +407,8 @@ def __ComputeMethodInfo(self, method_description, request, response,
                 method_description.get('mediaUpload'), method_id)
         method_info.supports_download = method_description.get(
             'supportsMediaDownload', False)
+        if method_description.get('apiVersion'):
+            method_info.api_version_param = method_description.get('apiVersion')
         self.__all_scopes.update(method_description.get('scopes', ()))
         for param, desc in method_description.get('parameters', {}).items():
             param = self.__names.CleanName(param)