diff --git a/.circleci/config.yml b/.circleci/config.yml
new file mode 100644
index 00000000..a33b2097
--- /dev/null
+++ b/.circleci/config.yml
@@ -0,0 +1,23 @@
+# This workflow will install Python dependencies, run tests and lint with a variety of Python versions
+version: 2.1
+
+orbs:
+  python: circleci/python@2.1.1
+
+jobs:
+  build_and_test:
+    executor: python/default
+    steps:
+      - checkout
+      - python/install-packages:
+          pkg-manager: pip
+      - run:
+          name: Build
+          command: python setup.py build
+      - run:
+          name: Run Tests
+          command: pytest
+workflows:
+  main:
+    jobs:
+      - build_and_test
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
index 9d3540de..029d1d25 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,4 +17,7 @@ __pycache__/
 
 # JS files
 */node_modules/
-*package-lock.json
\ No newline at end of file
+*package-lock.json
+
+# Build files
+build/
diff --git a/okta/request_executor.py b/okta/request_executor.py
index b21475a4..8d1cca2c 100644
--- a/okta/request_executor.py
+++ b/okta/request_executor.py
@@ -118,8 +118,8 @@ async def create_request(self, method: str, url: str, body: dict = None,
 
         # Build request
         # Get predetermined headers and build URL
-        headers.update(self._custom_headers)
-        headers.update(self._default_headers)
+        headers = {**self._custom_headers, **headers}
+        headers = {**self._default_headers, **headers}
         if self._config["client"]["orgUrl"] not in url:
             url = self._config["client"]["orgUrl"] + url
 
diff --git a/tests/unit/test_request_executor.py b/tests/unit/test_request_executor.py
index 6759ca99..fcba3dd7 100644
--- a/tests/unit/test_request_executor.py
+++ b/tests/unit/test_request_executor.py
@@ -1,6 +1,7 @@
 import aiohttp
 import asyncio
 import datetime
+import pytest
 import time
 
 from http import HTTPStatus
@@ -29,11 +30,13 @@ class MockHTTPRequest():
 
         def __call__(self, **params):
             self.request_info = params
-            self.headers = MultiDict({'Date': datetime.datetime.now(tz=datetime.timezone.utc).strftime('%a, %d %b %Y %H:%M:%S %Z'),
-                                      'Content-Type': 'application/json',
-                                      'X-Rate-Limit-Limit': 600,
-                                      'X-Rate-Limit-Remaining': 599,
-                                      'X-Rate-Limit-Reset': str(time.time())})
+            self.headers = MultiDict(
+                {'Date': datetime.datetime.now(tz=datetime.timezone.utc).strftime('%a, %d %b %Y %H:%M:%S %Z'),
+                 'Content-Type': 'application/json',
+                 'X-Rate-Limit-Limit': 600,
+                 'X-Rate-Limit-Remaining': 599,
+                 'X-Rate-Limit-Reset': str(time.time())}
+            )
             self.url = params['url']
             self.content_type = 'application/json'
             self.links = ''
@@ -95,17 +98,46 @@ def test_clear_empty_params():
     body = {'int_value': 0,
             'str_value': '0',
             'empty_str_value': '',
-            'list_value': [1,2,3],
+            'list_value': [1, 2, 3],
             'empty_list_value': [],
             'dict_value': {'int_value': 0},
             'empty_dict_value': {},
-            'nested_empty_dict_value': {'list_value': [1,2,3], 'empty_list_value': []},
+            'nested_empty_dict_value': {'list_value': [1, 2, 3], 'empty_list_value': []},
             'nested_empty_list_value': {'empty_list_value': []}}
 
     cleared_body = {'int_value': 0,
                     'str_value': '0',
-                    'list_value': [1,2,3],
+                    'list_value': [1, 2, 3],
                     'dict_value': {'int_value': 0},
-                    'nested_empty_dict_value': {'list_value': [1,2,3]}}
+                    'nested_empty_dict_value': {'list_value': [1, 2, 3]}}
 
     assert req_exec.clear_empty_params(body) == cleared_body
+
+
+@pytest.mark.parametrize(
+    "accept_header",
+    ["", "application/xml", "application/json",
+        "text/html", "application/xhtml+xml", "image/jpeg"]
+)
+@pytest.mark.asyncio
+async def test_overwrite_default_request_executor_headers(accept_header):
+    org_url = "https://test.okta.com"
+    token = "TOKEN"
+    config = {'client': {'orgUrl': org_url,
+                         'token': token,
+                         'rateLimit': {},
+                         'authorizationMode': None}}
+    req_exec = RequestExecutor(config=config, cache=None)
+
+    # overwrite headers if parameter present
+    header_overwrite = {'Accept': accept_header} if accept_header else {}
+    request, error = await req_exec.create_request(
+        'GET',
+        f'{org_url}/api/v1/users',
+        {},
+        header_overwrite,
+        {}
+    )
+    assert request is not None
+    assert request["headers"]["Accept"] ==\
+        accept_header if accept_header else "application/json"