regenerate docs
diff --git a/doc/pyOpenSSL.txt b/doc/pyOpenSSL.txt
index cd89173..fbc1fae 100644
--- a/doc/pyOpenSSL.txt
+++ b/doc/pyOpenSSL.txt
@@ -263,6 +263,8 @@
                  YYYYMMDDhhmmss+hhmm
                  YYYYMMDDhhmmss-hhmm
 
+          If no value exists for this field, None is returned.
+
    get_notAfter()
           Return a string giving the time after which the certificate is
           not valid. The string is formatted as an ASN1 GENERALIZEDTIME:
@@ -271,6 +273,8 @@
                  YYYYMMDDhhmmss+hhmm
                  YYYYMMDDhhmmss-hhmm
 
+          If no value exists for this field, None is returned.
+
    set_notBefore(when)
           Change the time before which the certificate is not valid. when
           is a string formatted as an ASN1 GENERALIZEDTIME: