diff --git a/src/clj_figlet/core.clj b/src/clj_figlet/core.clj
index 753923b..7b504b5 100644
--- a/src/clj_figlet/core.clj
+++ b/src/clj_figlet/core.clj
@@ -9,8 +9,10 @@
      :num-comments (Integer/parseInt (nth parts 5))}))
 
 (defn load-flf [file]
-  (let [lines      (str/split (slurp file) #"\n")
-        header     (parse-flf-header (first lines))
-        char-lines (drop (inc (:num-comments header)) lines)]
-    ))
-
+  (let [flf-file (slurp file)]
+    (if-not (= "flf2a" (subs flf-file 0 5))
+      (throw (new Exception (str "Not a valid flf font file: " file))))
+    (let [lines      (str/split (slurp file) #"\n")
+          header     (parse-flf-header (first lines))
+          char-lines (drop (inc (:num-comments header)) lines)]
+      )))