diff --git a/collects/macro-debugger/model/reductions-engine.rkt b/collects/macro-debugger/model/reductions-engine.rkt
index c51b318..5970a70 100644
--- a/collects/macro-debugger/model/reductions-engine.rkt
+++ b/collects/macro-debugger/model/reductions-engine.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 (require (for-syntax racket/base
-                     syntax/parse)
+                     syntax/parse
+                     syntax/parse/experimental/contract)
          racket/list
          racket/contract
          "deriv.rkt"