diff --git a/library/TRXC_Types.ttcn b/library/TRXC_Types.ttcn
index 37b8610..a87266e 100644
--- a/library/TRXC_Types.ttcn
+++ b/library/TRXC_Types.ttcn
@@ -68,7 +68,11 @@
 external function dec_TrxcMessage(in charstring id) return TrxcMessage
 	with { extension "prototype(convert) decode(TEXT)" };
 
-template (value) TrxcMessage ts_TRXC_FAKE_RSSI(uint8_t rssi, int16_t thresh := 0) := {
+/* rxlev2dbm(0..63) gives us [-110..-47], plus -10 dbm for noise */
+type integer TRXC_RSSI		(-120..-47);
+type integer TRXC_RSSI_THRESH	(-120..120);
+
+template (value) TrxcMessage ts_TRXC_FAKE_RSSI(TRXC_RSSI rssi, TRXC_RSSI_THRESH thresh := 0) := {
 	cmd := {
 		verb := "FAKE_RSSI",
 		params := { int2str(rssi), int2str(thresh) }