diff --git a/library/LAPDm_RAW_PT.ttcn b/library/LAPDm_RAW_PT.ttcn
index 77f0452..d0ad24b 100644
--- a/library/LAPDm_RAW_PT.ttcn
+++ b/library/LAPDm_RAW_PT.ttcn
@@ -39,7 +39,7 @@
 	/* directly switch to a dedicated channel (without RACH/IMM.ASS */
 	type record DCCH_switch_req {
 		ChannelDescription chan_desc,
-		L1ctlMA ma
+		L1ctlMA ma optional
 	}
 
 	type record DCCH_switch_res {