diff --git a/TCAP/asn_src/ITU/TC.asn b/TCAP/asn_src/ITU/TC.asn
index 34aca66..cfacf54 100644
--- a/TCAP/asn_src/ITU/TC.asn
+++ b/TCAP/asn_src/ITU/TC.asn
@@ -40,7 +40,7 @@ ReturnResult ::= SEQUENCE {
 	result SEQUENCE {
 		opcode Code,
 		result Param OPTIONAL
-	}
+	} OPTIONAL
 }
 
 ReturnError ::= SEQUENCE {