diff --git a/modules/luci-base/luasrc/cbi/datatypes.lua b/modules/luci-base/luasrc/cbi/datatypes.lua
index 99113e0b7a..b4206e98df 100644
--- a/modules/luci-base/luasrc/cbi/datatypes.lua
+++ b/modules/luci-base/luasrc/cbi/datatypes.lua
@@ -460,3 +460,7 @@ function dateyyyymmdd(val)
 	end
 	return false
 end
+
+function unique(val)
+	return true
+end