diff --git a/pycose/keys/cosekey.py b/pycose/keys/cosekey.py
index 2fddc1d..119840b 100644
--- a/pycose/keys/cosekey.py
+++ b/pycose/keys/cosekey.py
@@ -107,6 +107,7 @@ def from_pem_private_key(
 
         :param pem: PEM-encoded private key.
         :param password: Password to decrypt the key.
+        :param optional_params: Optional parameters to add to the key.
         :return: an initialized CoseKey object.
         """
         ext_key = load_pem_private_key(pem.encode(), password)
@@ -121,6 +122,7 @@ def from_pem_public_key(
         Initialize a COSE key from a PEM-encoded public key.
 
         :param pem: PEM-encoded public key.
+        :param optional_params: Optional parameters to add to the key.
         :return: an initialized CoseKey object.
         """
         ext_key = load_pem_public_key(pem.encode())