diff --git a/backplane-dns.lisp b/backplane-dns.lisp
index d397d10..ed57ea5 100644
--- a/backplane-dns.lisp
+++ b/backplane-dns.lisp
@@ -194,7 +194,9 @@
 
 (defun read-file-line (filename)
   (let ((input (open filename :if-does-not-exist nil)))
-    (read-line input)))
+    (if input
+        (read-line input)
+        (uiop:die 1 "unable to read file: ~A" filename))))
 
 (defun start-listener-with-env ()
   (backplane-dns-listen