diff --git a/pyDataverse/api.py b/pyDataverse/api.py
index 1ce6c38..8cce5a8 100644
--- a/pyDataverse/api.py
+++ b/pyDataverse/api.py
@@ -411,9 +411,14 @@ def _sync_request(
         kwargs = self._filter_kwargs(kwargs)
 
         try:
-            resp = method(**kwargs, auth=self.auth, follow_redirects=True, timeout=None)
+            resp: httpx.Response = method(
+                **kwargs, auth=self.auth, follow_redirects=True, timeout=None
+            )
             if resp.status_code == 401:
-                error_msg = resp.json()["message"]
+                try:
+                    error_msg = resp.json()["message"]
+                except json.JSONDecodeError:
+                    error_msg = resp.reason_phrase
                 raise ApiAuthorizationError(
                     "ERROR: HTTP 401 - Authorization error {0}. MSG: {1}".format(
                         kwargs["url"], error_msg
diff --git a/tests/api/test_api.py b/tests/api/test_api.py
index c8e7b72..817c4b3 100644
--- a/tests/api/test_api.py
+++ b/tests/api/test_api.py
@@ -217,3 +217,16 @@ def test_sword_api_requires_http_basic_auth(self):
             API_TOKEN = os.getenv("API_TOKEN")
             api = SwordApi(BASE_URL, api_token=API_TOKEN)
             assert isinstance(api.auth, httpx.BasicAuth)
+
+        def test_sword_api_can_authenticate(self):
+            BASE_URL = os.getenv("BASE_URL")
+            API_TOKEN = os.getenv("API_TOKEN")
+            api = SwordApi(BASE_URL, api_token=API_TOKEN)
+            response = api.get_service_document()
+            assert response.status_code == 200
+
+        def test_sword_api_cannot_authenticate_without_token(self):
+            BASE_URL = os.getenv("BASE_URL")
+            api = SwordApi(BASE_URL)
+            with pytest.raises(ApiAuthorizationError):
+                api.get_service_document()