diff --git a/OpenSSL/crypto.py b/OpenSSL/crypto.py
index efa1d91..95ccc18 100644
--- a/OpenSSL/crypto.py
+++ b/OpenSSL/crypto.py
@@ -1721,7 +1721,9 @@
 
         :param days: The number of days until the next update of this CRL.
         :type days: :py:data:`int`
+
         :param digest: The message digest to use
+        :type digest: :py:data:`str`
 
         :return: :py:data:`str`
         """
diff --git a/OpenSSL/test/test_crypto.py b/OpenSSL/test/test_crypto.py
index dacbf9e..5c4eac4 100644
--- a/OpenSSL/test/test_crypto.py
+++ b/OpenSSL/test/test_crypto.py
@@ -3017,6 +3017,10 @@
 
 
     def test_export_unknown_digest(self):
+        """
+        Calling :py:obj:`OpenSSL.CRL.export` with a unsupported digest results
+        in a :py:obj:`ValueError` being raised.
+        """
         crl = CRL()
         self.assertRaises(ValueError, crl.export, self.cert, self.pkey, FILETYPE_PEM, 10, "strange-digest")
 
diff --git a/doc/api/crypto.rst b/doc/api/crypto.rst
index b360e89..c5b7c33 100644
--- a/doc/api/crypto.rst
+++ b/doc/api/crypto.rst
@@ -724,10 +724,11 @@
     Add a Revoked object to the CRL, by value not reference.
 
 
-.. py:method:: CRL.export(cert, key[, type=FILETYPE_PEM][, days=100])
+.. py:method:: CRL.export(cert, key[, type=FILETYPE_PEM][, days=100][, digest='md5'])
 
     Use *cert* and *key* to sign the CRL and return the CRL as a string.
     *days* is the number of days before the next CRL is due.
+    *digest* is the algorithm that will be used to sign CRL.
 
 
 .. py:method:: CRL.get_revoked()