diff --git a/OpenSSL/crypto.py b/OpenSSL/crypto.py
index 60c34ce..75e3b42 100644
--- a/OpenSSL/crypto.py
+++ b/OpenSSL/crypto.py
@@ -1076,7 +1076,7 @@
         :param digest: The name of the message digest to use.
         :type digest: :py:class:`bytes`
 
-        :return: :py:data`None`
+        :return: :py:data:`None`
         """
         if not isinstance(pkey, PKey):
             raise TypeError("pkey must be a PKey instance")