diff --git a/host/chez/reader.ss b/host/chez/reader.ss
index de853bb..839da8b 100644
--- a/host/chez/reader.ss
+++ b/host/chez/reader.ss
@@ -645,8 +645,13 @@
   (cond
     ((eq? tag (keyword #f "#uuid")) (jolt-uuid-from-string form))
     ((eq? tag (keyword #f "#inst")) (jolt-inst-from-string form))
-    (else (jolt-throw (jolt-ex-info (string-append "No reader function for tag " (jolt-pr-str tag))
-                                    (empty-pmap))))))
+    ;; No registered reader: throw a clean, catchable ex-info naming the tag, like
+    ;; the JVM's "No reader function for tag foobar" (empty-pmap is a VALUE — the
+    ;; old (empty-pmap) applied it as a procedure and crashed the Chez VM).
+    (else (let* ((nm (keyword-t-name tag))
+                 (bare (if (and (> (string-length nm) 0) (char=? (string-ref nm 0) #\#))
+                           (substring nm 1 (string-length nm)) nm)))
+            (jolt-throw (jolt-ex-info (string-append "No reader function for tag " bare) empty-pmap))))))
 
 (def-var! "clojure.core" "read-string" jolt-read-string)
 (def-var! "clojure.core" "__parse-next" jolt-parse-next)
diff --git a/test/chez/corpus.edn b/test/chez/corpus.edn
index 42b9d69..2bb10c7 100644
--- a/test/chez/corpus.edn
+++ b/test/chez/corpus.edn
@@ -3063,4 +3063,7 @@
   {:suite "interop / java.io streams" :label "BufferedReader over StringReader readLine" :expected "[\"a\" \"b\" nil]" :actual "(let [r (java.io.BufferedReader. (java.io.StringReader. \"a\\nb\\n\"))] [(.readLine r) (.readLine r) (.readLine r)])"}
   {:suite "interop / java.io streams" :label "instance? InputStream" :expected "true" :actual "(instance? java.io.InputStream (java.io.ByteArrayInputStream. (.getBytes \"x\")))"}
   {:suite "interop / java.io streams" :label "FileOutputStream then FileInputStream round-trip" :expected "90" :actual "(let [f (java.io.File/createTempFile \"jc\" \".t\") o (java.io.FileOutputStream. f)] (.write o (byte-array [90])) (.close o) (let [in (java.io.FileInputStream. f) b (.read in)] (.close in) (.delete f) b))"}
+  {:suite "clojure.edn / unknown tags" :label "unknown tag throws naming the tag" :expected "\"No reader function for tag foobar\"" :actual "(do (require (quote [clojure.edn :as e1])) (try (e1/read-string \"#foobar 1\") (catch Exception e (ex-message e))))"}
+  {:suite "clojure.edn / unknown tags" :label "object tag throws naming the tag" :expected "\"No reader function for tag object\"" :actual "(do (require (quote [clojure.edn :as e2])) (try (e2/read-string \"#object [1 2 3]\") (catch Exception e (ex-message e))))"}
+  {:suite "clojure.edn / unknown tags" :label ":default opt handles an unknown tag" :expected "[\"foobar\" 9]" :actual "(do (require (quote [clojure.edn :as e3])) (e3/read-string {:default (fn [t v] [(name t) v])} \"#foobar 9\"))"}
 ]