diff --git a/library/Osmocom_CTRL_Types.ttcn b/library/Osmocom_CTRL_Types.ttcn
index 5d6ddae..4d2406d 100644
--- a/library/Osmocom_CTRL_Types.ttcn
+++ b/library/Osmocom_CTRL_Types.ttcn
@@ -55,7 +55,7 @@
 	CtrlResponse	resp,
 	CtrlError	err,
 	CtrlTrap	trap
-};
+} with { variant "BEGIN('')" };
 
 external function enc_CtrlMessage(in CtrlMessage id) return charstring
 	with { extension "prototype(convert) encode(TEXT)"};