diff --git a/lemur/certificates/views.py b/lemur/certificates/views.py
index 3de200d5..4bc317f1 100644
--- a/lemur/certificates/views.py
+++ b/lemur/certificates/views.py
@@ -90,7 +90,7 @@ def private_key_str(value, name):
     :return: :raise ValueError:
     """
     try:
-        serialization.load_pem_private_key(str(value), backend=default_backend())
+        serialization.load_pem_private_key(str(value), None, backend=default_backend())
     except Exception as e:
         raise ValueError("The parameter '{0}' needs to be a valid RSA private key".format(name))
     return value