diff --git a/tests/plugin/kdc_test_plugin.c b/tests/plugin/kdc_test_plugin.c
index ff33b5f72..0effd9783 100644
--- a/tests/plugin/kdc_test_plugin.c
+++ b/tests/plugin/kdc_test_plugin.c
@@ -39,7 +39,8 @@ pac_generate(void *ctx,
 
     krb5_warnx(context, "pac generate");
 
-    data.data = "\x00\x01";
+    /* used read-only by krb5_pac_add_buffer */
+    data.data = rk_UNCONST("\x00\x01");
     data.length = 2;
 
     ret = krb5_pac_init(context, pac);