diff --git a/collects/plai/private/datatype-core.ss b/collects/plai/private/datatype-core.ss
index 6933e880c1..ace7e723b5 100644
--- a/collects/plai/private/datatype-core.ss
+++ b/collects/plai/private/datatype-core.ss
@@ -8,7 +8,8 @@
 (module datatype-core mzscheme
   (require (lib "pconvert-prop.ss")
 	   (lib "contract.ss" "mzlib" "private")
-           (lib "contract-util.ss" "mzlib" "private"))
+           (lib "contract-util.ss" "mzlib" "private")
+           (lib "contract-arrow.ss" "mzlib" "private"))
   (require-for-syntax "core-utils.ss")
 
   (provide define-datatype-core