diff --git a/dns/types/header.scm b/dns/types/header.scm
index 8f4c3cc889461492014a98e6781133306399d523..8e2b89be82bfa2db899fcc3c45d56fe96fae4203 100644
--- a/dns/types/header.scm
+++ b/dns/types/header.scm
@@ -27,7 +27,7 @@
           (opcode default: 'QUERY
                   type: (or (uint? 4) (assq (@ (dns enum) opcode-types))))
           (aa type: boolean?) (tc type: boolean?) (rd type: boolean?) (ra type: boolean?)
-          (z default: 0 type: zero?)
+          (z default: 0)
           (rcode default: 'NOERROR type: (or (uint? 4) (assq (@ (dns enum) rcode-types))))
           ;; lengths
           (qdcount default: 0 type: u16?) (ancount default: 0 type: u16?)