diff --git a/backplane-server.lisp b/backplane-server.lisp
index 5fa6c99..b441143 100644
--- a/backplane-server.lisp
+++ b/backplane-server.lisp
@@ -40,14 +40,14 @@
 
 (defmethod render-result ((res result/success))
   (with-slots (message msg-id) res
-    (cl-json:encode-json
+    (cl-json:encode-json-to-string
      `((STATUS  . "OK")
        (MESSAGE . ,message)
        (MSGID   . ,msg-id)))))
 
 (defmethod render-result ((res result/error))
   (with-slots (message msg-id) res
-    (cl-json:encode-json
+    (cl-json:encode-json-to-string
      `((STATUS  . "ERROR")
        (MESSAGE . ,message)
        (MSGID   . ,msg-id)))))