diff --git a/package/gluon-core/check_site.lua b/package/gluon-core/check_site.lua
index 61c7ae09..c78e89dc 100644
--- a/package/gluon-core/check_site.lua
+++ b/package/gluon-core/check_site.lua
@@ -19,7 +19,7 @@ need_string 'timezone'
 
 need_string_array('ntp_servers', false)
 
-need_string_match('prefix6', '^[%x:]+/%d+$')
+need_string_match('prefix6', '^[%x:]+/64$')
 
 
 for _, config in ipairs({'wifi24', 'wifi5'}) do