diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index 1e8aeba..399d693 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -1541,6 +1541,13 @@
 
         .. versionadded:: 1.0
 
+        .. note::
+
+            This method should be used if the issuer certificate does not
+            contain a :class:`~cryptography.x509.SubjectKeyIdentifier`.
+            Otherwise, use
+            :meth:`~cryptography.x509.AuthorityKeyIdentifier.from_issuer_subject_key_identifier`.
+
         Creates a new AuthorityKeyIdentifier instance using the public key
         provided to generate the appropriate digest. This should be the
         **issuer's public key**. The resulting object will contain
@@ -1572,6 +1579,11 @@
 
         .. versionadded:: 1.3
 
+        .. note::
+            This method should be used if the issuer certificate contains a
+            :class:`~cryptography.x509.SubjectKeyIdentifier`.  Otherwise, use
+            :meth:`~cryptography.x509.AuthorityKeyIdentifier.from_issuer_public_key`.
+
         Creates a new AuthorityKeyIdentifier instance using the
         SubjectKeyIdentifier from the issuer certificate. The resulting object
         will contain