diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 332bc74..e27490d 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -168,8 +168,10 @@
   a basic constraints extension with CA set to false and a path length of zero
   in violation of :rfc:`5280`.
 * ``tls-feature-ocsp-staple.pem`` - A certificate issued by Let's Encrypt that
-  contains a TLS Feature extension with the ``status_request`` feature (commonly
-  known as OCSP Must-Staple).
+  contains a TLS Feature extension with the ``status_request`` feature
+  (commonly known as OCSP Must-Staple).
+* ``unique-identifier.pem`` - A certificate containing
+  a distinguished name with an ``x500UniqueIdentifier``.
 
 Custom X.509 Vectors
 ~~~~~~~~~~~~~~~~~~~~
diff --git a/vectors/cryptography_vectors/x509/unique_identifier.pem b/vectors/cryptography_vectors/x509/unique_identifier.pem
new file mode 100644
index 0000000..178fb0a
--- /dev/null
+++ b/vectors/cryptography_vectors/x509/unique_identifier.pem
@@ -0,0 +1,11 @@
+-----BEGIN CERTIFICATE-----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==
+-----END CERTIFICATE-----