diff --git a/src/clj/coffi/mem.clj b/src/clj/coffi/mem.clj
index eb8fb7c..b574792 100644
--- a/src/clj/coffi/mem.clj
+++ b/src/clj/coffi/mem.clj
@@ -1922,7 +1922,7 @@
   (let [invalid-typenames (filter #(try (c-layout (first %)) nil (catch Exception e (first %))) (partition 2 members))]
     (cond
       (odd? (count members)) (throw (Exception. "uneven amount of members supplied. members have to be typed and are required to be supplied in the form of `typename member-name`. the typename has to be coffi typename, like `:coffi.mem/int` or `[:coffi.mem/array :coffi.mem/byte 3]`"))
-      (seq invalid-typenames) (throw (Exception. (str "invalid typename/s " (print-str invalid-typenames) ". typename has to be coffi typename, like `:coffi.mem/int` or `[:coffi.mem/array :coffi.mem/byte 3]`")))
+      (seq invalid-typenames) (throw (Exception. (str "invalid typename/s " (print-str invalid-typenames) ". typename has to be coffi typename, like `:coffi.mem/int` or `[:coffi.mem/array :coffi.mem/byte 3]`. The type/s you referenced also might not be defined. In case of a custom type, ensure that you use the correctly namespaced keyword to refer to it.")))
       :else
       (let [coffi-typename (keyword (str *ns*) (str typename))
             typed-symbols (->>