diff --git a/deepomatic/api/exceptions.py b/deepomatic/api/exceptions.py
index 6470c98..97df5e4 100644
--- a/deepomatic/api/exceptions.py
+++ b/deepomatic/api/exceptions.py
@@ -32,6 +32,12 @@ class DeepomaticException(Exception):
     def __init__(self, msg):
         super(DeepomaticException, self).__init__(msg)
 
+###############################################################################
+
+
+class CredentialsNotFound(DeepomaticException):
+    pass
+
 
 ###############################################################################
 
diff --git a/deepomatic/api/http_helper.py b/deepomatic/api/http_helper.py
index ba055f3..beb2656 100644
--- a/deepomatic/api/http_helper.py
+++ b/deepomatic/api/http_helper.py
@@ -30,7 +30,8 @@
 
 import requests
 from deepomatic.api.exceptions import (BadStatus, ServerError,
-                                       ClientError, DeepomaticException)
+                                       ClientError, DeepomaticException,
+                                       CredentialsNotFound)
 from deepomatic.api.http_retry import HTTPRetry
 from deepomatic.api.version import __title__, __version__
 from requests.structures import CaseInsensitiveDict
@@ -76,7 +77,7 @@ def __init__(self, app_id=None, api_key=None, verify_ssl=None,
         if api_key is None:
             api_key = os.getenv('DEEPOMATIC_API_KEY')
         if api_key is None:
-            raise DeepomaticException("Please specify 'api_key' either by passing it to the client"
+            raise CredentialsNotFound("Please specify 'api_key' either by passing it to the client"
                                       " or by defining the DEEPOMATIC_API_KEY environment variable.")
 
         if version is None or version == '':