diff --git a/lib/d/test/openssl.test.cnf b/lib/d/test/openssl.test.cnf
new file mode 100644
index 0000000..2ada30b
--- /dev/null
+++ b/lib/d/test/openssl.test.cnf
@@ -0,0 +1,14 @@
+[ req ]
+default_bits = 2048
+default_keyfile = server-private-key.pem
+distinguished_name = req_distinguished_name
+x509_extensions = v3_ca
+prompt = no
+
+[ req_distinguished_name ]
+CN = localhost
+
+[ v3_ca ]
+# Add ::1 to the list of allowed IPs so we can use ::1 to explicitly connect
+# to localhost via IPv6.
+subjectAltName = IP:::1