diff --git a/library/L1CTL_PortType.ttcn b/library/L1CTL_PortType.ttcn
index dd5abc9..b82419e 100644
--- a/library/L1CTL_PortType.ttcn
+++ b/library/L1CTL_PortType.ttcn
@@ -26,6 +26,9 @@
 		T.start
 		alt {
 			[] pt.receive(t_L1CTL_FBSB_CONF(0)) {};
+			[] pt.receive(t_L1CTL_FBSB_CONF(?)) {
+				setverdict(fail, "FBSB Failed with non-zero return code");
+				};
 			[] pt.receive { repeat; };
 			[] T.timeout { setverdict(fail, "Timeout in FBSB") };
 		}