fix docs
diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index 3051308..12fee80 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -2435,7 +2435,7 @@
     .. attribute:: POLICY_CONSTRAINTS
 
         Corresponds to the dotted string ``"2.5.29.36"``. The identifier for the
-        :class:`PolicyConstraints` extension type.
+        :class:`~cryptography.x509.PolicyConstraints` extension type.
 
 
 .. class:: CRLEntryExtensionOID