diff --git a/miniflux.py b/miniflux.py
index 9d25c58..2157046 100644
--- a/miniflux.py
+++ b/miniflux.py
@@ -39,6 +39,7 @@ class ClientError(Exception):
     def __init__(self, response: requests.Response):
         self.status_code = response.status_code
         self._response = response
+        super().__init__(self.get_error_reason())
 
     def get_error_reason(self) -> str:
         """
diff --git a/tests/test_client.py b/tests/test_client.py
index c4aca63..d4a099d 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -48,6 +48,21 @@ def test_get_error_reason(self):
         self.assertEqual(error.status_code, 404)
         self.assertEqual(error.get_error_reason(), "some error")
 
+    def test_error_str_with_json_reason(self):
+        response = mock.Mock()
+        response.status_code = 404
+        response.headers = {"Content-Type": "application/json"}
+        response.json.return_value = {"error_message": "feed not found"}
+        error = ResourceNotFound(response)
+        self.assertEqual(str(error), "feed not found")
+
+    def test_error_str_without_json_reason(self):
+        response = mock.Mock()
+        response.status_code = 500
+        response.headers = {}
+        error = ServerError(response)
+        self.assertEqual(str(error), "status_code=500")
+
     def test_default_session_not_shared(self):
         client_one = miniflux.Client("http://localhost", api_key="token-one")
         client_two = miniflux.Client("http://localhost", api_key="token-two")