1 files changed, 12 insertions, 6 deletions
diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index ca8b1b62..eb6654b0 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -10,13 +10,14 @@ import contextlib
 import itertools
 from contextlib import contextmanager
 
-import asn1crypto.core
-
 import six
 from six.moves import range
 
 from cryptography import utils, x509
 from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
+from cryptography.hazmat._der import (
+    INTEGER, NULL, SEQUENCE, encode_der, encode_der_integer
+)
 from cryptography.hazmat.backends.interfaces import (
     CMACBackend, CipherBackend, DERSerializationBackend, DHBackend, DSABackend,
     EllipticCurveBackend, HMACBackend, HashBackend, PBKDF2HMACBackend,
@@ -26,7 +27,7 @@ from cryptography.hazmat.backends.openssl import aead
 from cryptography.hazmat.backends.openssl.ciphers import _CipherContext
 from cryptography.hazmat.backends.openssl.cmac import _CMACContext
 from cryptography.hazmat.backends.openssl.decode_asn1 import (
-    _CRL_ENTRY_REASON_ENUM_TO_CODE, _Integers
+    _CRL_ENTRY_REASON_ENUM_TO_CODE
 )
 from cryptography.hazmat.backends.openssl.dh import (
     _DHParameters, _DHPrivateKey, _DHPublicKey, _dh_params_dup
@@ -1008,12 +1009,17 @@ class Backend(object):
             value = _encode_asn1_str_gc(self, extension.value.value)
             return self._create_raw_x509_extension(extension, value)
         elif isinstance(extension.value, x509.TLSFeature):
-            asn1 = _Integers([x.value for x in extension.value]).dump()
+            asn1 = encode_der(
+                SEQUENCE,
+                *[
+                    encode_der(INTEGER, encode_der_integer(x.value))
+                    for x in extension.value
+                ]
+            )
             value = _encode_asn1_str_gc(self, asn1)
             return self._create_raw_x509_extension(extension, value)
         elif isinstance(extension.value, x509.PrecertPoison):
-            asn1 = asn1crypto.core.Null().dump()
-            value = _encode_asn1_str_gc(self, asn1)
+            value = _encode_asn1_str_gc(self, encode_der(NULL))
             return self._create_raw_x509_extension(extension, value)
         else:
             try: