diff --git a/src/runner/koans.clj b/src/runner/koans.clj
index fcbdaf8..bc7c514 100644
--- a/src/runner/koans.clj
+++ b/src/runner/koans.clj
@@ -47,9 +47,10 @@
       (println "Problem in" file-path)
       (println "---------------------")
       (println "Assertion failed!")
-      (println (.replaceFirst (.getMessage (.getCause e))
-                              "^Assert failed: "
-                              ""))
+      (let [actual-error (or (.getCause e) e)
+            message (or (.getMessage actual-error)
+                        (.toString actual-error))]
+        (println (.replaceFirst message "^Assert failed: " "")))
       false)))
 
 (defn namaste []