diff --git a/guix/openpgp.scm b/guix/openpgp.scm
index 9370c8ada8..b74f8ff5bf 100644
--- a/guix/openpgp.scm
+++ b/guix/openpgp.scm
@@ -136,6 +136,7 @@ (define-condition-type &openpgp-unrecognized-packet-error &openpgp-error
 
 ;; Error raised when reading an invalid signature packet.
 (define-condition-type &openpgp-invalid-signature-error &openpgp-error
+  openpgp-invalid-signature-error?
   (port openpgp-invalid-signature-error-port))