diff --git a/source/app/controllers/pacs/cfdi_cert.py b/source/app/controllers/pacs/cfdi_cert.py
index 642e13d..2a0a7fe 100644
--- a/source/app/controllers/pacs/cfdi_cert.py
+++ b/source/app/controllers/pacs/cfdi_cert.py
@@ -223,7 +223,8 @@ class SATCertificate(object):
         path.write_text(obj.key_enc)
         args = f'openssl rsa -inform PEM -outform PEM -in "{str(path)}" -passin pass:{token}'
         pem = subprocess.check_output(args, shell=True).decode()
-        key = serialization.load_pem_private_key(pem.encode(), password=None)
+        key = serialization.load_pem_private_key(
+            pem.encode(), password=None, default_backend())
 
         digest = hashes.Hash(hashes.SHA512(), default_backend())
         digest.update(obj.rfc.encode())