diff --git a/src/test/clojure/clojure/data/json_test.clj b/src/test/clojure/clojure/data/json_test.clj
index 6779ad2..2602c81 100644
--- a/src/test/clojure/clojure/data/json_test.clj
+++ b/src/test/clojure/clojure/data/json_test.clj
@@ -136,7 +136,7 @@
                     :key-fn keyword
                     :value-fn (fn [k v]
                                 (if (= :date k)
-                                  (java.sql.Date/valueOf v)
+                                  (java.sql.Date/valueOf ^String v)
                                   v))))))
 
 (deftest omit-values