diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 9395202..4c0063b 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -227,6 +227,9 @@
   request for an RSA 2048 bit key containing containing an unsupported
   extension type marked critical. The OID was encoded as "1.2.3.4"
   with an ``extnValue`` of "value".
+* ``basic_constraints.pem`` - A certificate signing request for a RSA
+  2048 bit key containing a basic constraints extension marked as
+  critical.
 
 Hashes
 ~~~~~~
diff --git a/vectors/cryptography_vectors/x509/requests/basic_constraints.pem b/vectors/cryptography_vectors/x509/requests/basic_constraints.pem
new file mode 100644
index 0000000..7169cda
--- /dev/null
+++ b/vectors/cryptography_vectors/x509/requests/basic_constraints.pem
@@ -0,0 +1,64 @@
+Certificate Request:
+    Data:
+        Version: 2 (0x2)
+        Subject: C=US, ST=Texas, L=Austin, O=PyCA, CN=cryptography.io
+        Subject Public Key Info:
+            Public Key Algorithm: rsaEncryption
+            RSA Public Key: (2048 bit)
+                Modulus (2048 bit):
+                    00:a4:1a:ae:63:a2:ad:23:0a:b7:a2:f0:0e:50:fd:
+                    96:e1:02:96:05:07:72:c8:96:a7:d6:a9:f6:19:fd:
+                    61:98:9a:ca:98:5c:41:69:0c:f2:f8:27:f2:c4:7d:
+                    fe:6d:08:9e:f7:99:2c:f7:ad:45:97:97:c3:eb:4c:
+                    d7:03:e1:32:27:77:be:73:74:3b:62:1f:66:c7:83:
+                    3c:44:45:76:a8:f1:34:00:84:fd:43:f8:2e:95:00:
+                    2f:34:f5:c9:d6:67:44:e1:65:42:42:c1:53:5f:7c:
+                    47:b2:65:a6:d5:ad:c8:9a:13:0b:58:c4:b9:42:c7:
+                    4d:76:c0:99:57:9d:b0:33:ec:f8:dd:a3:61:86:1f:
+                    df:bd:d8:56:ae:0d:bf:41:c8:b1:69:8a:2a:df:cf:
+                    2a:05:25:8a:34:6c:32:7e:8c:73:fa:41:1a:57:90:
+                    3d:5f:89:e1:b4:c6:bf:96:50:b7:62:fc:f7:20:13:
+                    6d:25:cc:b0:4f:3d:4b:85:d5:31:4a:a2:33:f9:f5:
+                    1f:e9:c1:e8:03:29:b3:df:65:51:80:27:2b:3e:d3:
+                    83:b2:fa:80:1b:03:43:56:07:26:f0:e9:58:64:bb:
+                    dc:7e:fd:c1:88:e1:10:54:4e:a3:f6:67:6c:c9:54:
+                    3d:9c:8d:62:43:be:31:77:d4:c3:ee:39:3c:b0:eb:
+                    e5:ab
+                Exponent: 65537 (0x10001)
+        Attributes:
+        Requested Extensions:
+            X509v3 Basic Constraints: critical
+                CA:TRUE, pathlen:1
+    Signature Algorithm: sha1WithRSAEncryption
+        0a:8a:70:98:1c:68:65:04:bb:6b:0c:93:90:03:e8:94:21:08:
+        1d:af:e6:59:2a:27:b1:f7:80:c3:aa:0a:dd:8b:07:67:7e:cf:
+        ac:99:c7:c9:70:d8:f2:13:32:25:b9:03:7d:b7:37:da:f4:d6:
+        43:00:be:80:fd:7d:6d:05:f7:a0:e8:3e:69:8a:b7:44:46:3c:
+        58:87:28:72:1e:eb:31:50:26:25:39:0e:57:85:b5:28:a2:6a:
+        0d:f5:88:70:f4:bc:81:d6:87:4e:f2:ca:64:1b:86:d5:04:2d:
+        1e:d6:32:00:23:04:8b:b0:9a:a9:8c:5b:60:2d:9e:ea:57:7a:
+        d2:e3:b4:f0:f4:0c:08:54:af:91:e3:b4:61:51:91:7e:60:4f:
+        0a:6e:db:65:38:1a:4f:35:07:e7:08:0d:0a:39:3e:7b:4a:bf:
+        03:f6:6e:5b:f4:47:95:53:22:21:b9:91:db:0e:76:f1:0f:6f:
+        82:a5:0f:b7:65:cf:19:12:9e:67:4e:5f:c1:b2:a7:02:d7:e4:
+        6a:55:de:35:52:32:4d:45:ab:b3:fc:82:3d:6d:65:9c:be:6c:
+        81:9a:10:9a:22:f8:75:de:9c:f4:61:de:6c:82:3a:5f:51:f4:
+        7b:b7:14:68:0b:ac:2b:16:76:46:5e:3c:bb:03:dd:dc:12:17:
+        70:06:4b:3c
+-----BEGIN CERTIFICATE REQUEST-----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+-----END CERTIFICATE REQUEST-----