diff --git a/pkgs/compatibility-pkgs/compatibility-lib/mzlib/private/contract-object.rkt b/pkgs/compatibility-pkgs/compatibility-lib/mzlib/private/contract-object.rkt
index 6aedcbb..c2b6906 100644
--- a/pkgs/compatibility-pkgs/compatibility-lib/mzlib/private/contract-object.rkt
+++ b/pkgs/compatibility-pkgs/compatibility-lib/mzlib/private/contract-object.rkt
@@ -4,6 +4,7 @@
          racket/contract/private/misc
          racket/contract/private/prop
          racket/private/class-internal
+         racket/private/class-c-old
          "contract-arr-checks.rkt")
 
 (require (for-syntax racket/base