diff --git a/src/spectator/dsl/memoize.cr b/src/spectator/dsl/memoize.cr
index 0e6b0aa..788a610 100644
--- a/src/spectator/dsl/memoize.cr
+++ b/src/spectator/dsl/memoize.cr
@@ -1,4 +1,5 @@
 require "../lazy_wrapper"
+require "./reserved"
 
 module Spectator::DSL
   # DSL methods for defining test values (subjects).