1 files changed, 4 insertions, 0 deletions
diff --git a/src/cryptography/x509.py b/src/cryptography/x509.py
index 21e18ddd..24d501e5 100644
--- a/src/cryptography/x509.py
+++ b/src/cryptography/x509.py
@@ -1468,6 +1468,10 @@ class CertificateSigningRequestBuilder(object):
         """
         if isinstance(extension, BasicConstraints):
             extension = Extension(OID_BASIC_CONSTRAINTS, critical, extension)
+        elif isinstance(extension, SubjectAlternativeName):
+            extension = Extension(
+                OID_SUBJECT_ALTERNATIVE_NAME, critical, extension
+            )
         else:
             raise NotImplementedError('Unsupported X.509 extension.')
         # TODO: This is quadratic in the number of extensions