diff --git a/src/babashka/impl/clojure/tools/reader.clj b/src/babashka/impl/clojure/tools/reader.clj
index 40df6b56..acfd528f 100644
--- a/src/babashka/impl/clojure/tools/reader.clj
+++ b/src/babashka/impl/clojure/tools/reader.clj
@@ -16,8 +16,8 @@
     :location? seq?
     :end-location false}))
 
-(def default-data-reader-fn (sci/new-dynamic-var '*default-data-reader-fn* {:ns rns}))
-(def alias-map (sci/new-dynamic-var '*alias-map* {:ns rns}))
+(def default-data-reader-fn (sci/new-dynamic-var '*default-data-reader-fn* nil {:ns rns}))
+(def alias-map (sci/new-dynamic-var '*alias-map* nil {:ns rns}))
 
 (defn resolve-tag [sym]
   ;; https://github.com/clojure/tools.reader/blob/ff18b1b872398a99e3e2941a0ed9abc0c2dec151/src/main/clojure/clojure/tools/reader.clj#L858