diff --git a/scheme/cyclone/cgen.sld b/scheme/cyclone/cgen.sld
index 3232de6d..6202bcc3 100644
--- a/scheme/cyclone/cgen.sld
+++ b/scheme/cyclone/cgen.sld
@@ -512,6 +512,7 @@
      ((eq? p 'Cyc-get-cvar)          "Cyc_get_cvar")
      ((eq? p 'Cyc-set-cvar!)         "Cyc_set_cvar")
      ((eq? p 'Cyc-cvar?)             "Cyc_is_cvar")
+     ; TODO: ((eq? p 'Cyc-opaque?)           "Cyc_is_opaque")
      ((eq? p 'Cyc-has-cycle?)        "Cyc_has_cycle")
      ((eq? p 'Cyc-spawn-thread!)     "Cyc_spawn_thread")
      ((eq? p 'Cyc-end-thread!)       "Cyc_end_thread")