diff --git a/pam_yubico.c b/pam_yubico.c
index 35abbb2..e63d9a6 100644
--- a/pam_yubico.c
+++ b/pam_yubico.c
@@ -695,6 +695,9 @@ pam_sm_authenticate (pam_handle_t * pamh,
       goto done;
     }
 
+  if (cfg->client_key)
+    ykclient_set_verify_signature (ykc, 1);
+
   if (cfg->capath)
     ykclient_set_ca_path (ykc, cfg->capath);