diff --git a/acme/acme/crypto_util.py b/acme/acme/crypto_util.py
index 8e8f73c54..062a25ca9 100644
--- a/acme/acme/crypto_util.py
+++ b/acme/acme/crypto_util.py
@@ -22,7 +22,7 @@ import warnings
 from cryptography import x509
 from cryptography.hazmat.primitives.hashes import SHA256
 from cryptography.hazmat.primitives.asymmetric.dsa import DSAPrivateKey
-from cryptography.hazmat.primitives.asymmetric.types import CertificateIssuerPrivateKeyTypes 
+from cryptography.hazmat.primitives.asymmetric.types import CertificateIssuerPrivateKeyTypes
 from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKey
 from cryptography.hazmat.primitives.serialization import Encoding
 from cryptography.hazmat.primitives.serialization import load_pem_private_key