diff --git a/library/RLCMAC_CSN1_Types.ttcn b/library/RLCMAC_CSN1_Types.ttcn
index a14577a..d41f9e1 100644
--- a/library/RLCMAC_CSN1_Types.ttcn
+++ b/library/RLCMAC_CSN1_Types.ttcn
@@ -824,7 +824,7 @@
 	/* 12.13 Power Control Parameters */
 	type record ZeroOneGamma {
 		BIT1		gamma_present,
-		uint5_t		gamma
+		uint5_t		gamma optional
 	} with {
 		variant (gamma) "PRESENCE (gamma_present = '1'B)"
 	};