diff --git a/library/MGCP_Types.ttcn b/library/MGCP_Types.ttcn
index 9d1a4e1..6bb266e 100644
--- a/library/MGCP_Types.ttcn
+++ b/library/MGCP_Types.ttcn
@@ -121,5 +121,16 @@
 	external function dec_MgcpMessage(in charstring  id) return MgcpMessage
 		with { extension "prototype(convert) decode(TEXT)" };
 
+	/* IANA / 3gpp assigned payload type numbers */
+	type enumerated SDP_FIELD_PayloadType {
+		PT_PCMU(0),
+		PT_GSM(3),
+		PT_PCMA(8),
+		PT_G729(18),
+		PT_GSMEFR(110),
+		PT_GSMHR(111),
+		PT_AMR(112),
+		PT_AMRWB(113)
+	}
 
 } with { encode "TEXT" }