diff --git a/OpenSSL/crypto.py b/OpenSSL/crypto.py
index c7bdabc..1b1058e 100644
--- a/OpenSSL/crypto.py
+++ b/OpenSSL/crypto.py
@@ -1,5 +1,6 @@
-from time import time
+from time import time, strptime
 from base64 import b16encode
+from calendar import timegm
 from functools import partial
 from operator import __eq__, __ne__, __lt__, __le__, __gt__, __ge__
 from warnings import warn as _warn
@@ -1161,10 +1162,10 @@
         :return: True if the certificate has expired, false otherwise
         """
         now = int(time())
-        notAfter = _lib.X509_get_notAfter(self._x509)
-        return _lib.ASN1_UTCTIME_cmp_time_t(
-            _ffi.cast('ASN1_UTCTIME*', notAfter), now) < 0
+        notAfter = self.get_notAfter().decode('utf-8')
+        notAfterSecs = timegm(strptime(notAfter, '%Y%m%d%H%M%SZ'))
 
+        return now > notAfterSecs
 
     def _get_boundary_time(self, which):
         return _get_asn1_time(which(self._x509))
diff --git a/OpenSSL/test/test_crypto.py b/OpenSSL/test/test_crypto.py
index 73e9cc7..b817451 100644
--- a/OpenSSL/test/test_crypto.py
+++ b/OpenSSL/test/test_crypto.py
@@ -1562,19 +1562,29 @@
         cert.gmtime_adj_notAfter(2)
         self.assertFalse(cert.has_expired())
 
+    def test_root_has_not_expired(self):
+        """
+        :py:obj:`X509Type.has_expired` returns :py:obj:`False` if the certificate's not-after
+        time is in the future.
+        """
+        cert = load_certificate(FILETYPE_PEM, root_cert_pem)
+        self.assertFalse(cert.has_expired())
+
 
     def test_digest(self):
         """
         :py:obj:`X509.digest` returns a string giving ":"-separated hex-encoded words
         of the digest of the certificate.
         """
-        cert = X509()
+        cert = load_certificate(FILETYPE_PEM, root_cert_pem)
         self.assertEqual(
             # This is MD5 instead of GOOD_DIGEST because the digest algorithm
             # actually matters to the assertion (ie, another arbitrary, good
             # digest will not product the same digest).
+            # Digest verified with the command:
+            # openssl x509 -in root_cert.pem -noout -fingerprint -md5
             cert.digest("MD5"),
-            b("A8:EB:07:F8:53:25:0A:F2:56:05:C5:A5:C4:C4:C7:15"))
+            b("19:B3:05:26:2B:F8:F2:FF:0B:8F:21:07:A8:28:B8:75"))
 
 
     def _extcert(self, pkey, extensions):
@@ -1587,6 +1597,7 @@
         cert.set_notAfter(when)
 
         cert.add_extensions(extensions)
+        cert.sign(pkey, 'sha1')
         return load_certificate(
             FILETYPE_PEM, dump_certificate(FILETYPE_PEM, cert))