diff --git a/util/uuid.lua b/util/uuid.lua
index 54c44c0..851167d 100644
--- a/util/uuid.lua
+++ b/util/uuid.lua
@@ -27,7 +27,7 @@ end
 
 function mail.new_uuid()
     local template ='xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
-    local candidate_uuid = ""
+    local candidate_uuid
     repeat
         candidate_uuid = string.gsub(template, '[xy]',
             function (c)