diff --git a/P25/lc/tsbk/IOSP_ACK_RSP.cs b/P25/lc/tsbk/IOSP_ACK_RSP.cs
index 53e0701..b709de7 100644
--- a/P25/lc/tsbk/IOSP_ACK_RSP.cs
+++ b/P25/lc/tsbk/IOSP_ACK_RSP.cs
@@ -33,7 +33,7 @@ namespace fnecore.P25.LC.TSBK
         /// <param name="srcId"></param>
         /// <param name="aivFlag"></param>
         /// <param name="service"></param>
-        public IOSP_ACK_RSP(uint dstId, uint srcId, bool aivFlag, byte service)
+        public IOSP_ACK_RSP(uint dstId = 0, uint srcId = 0, bool aivFlag = false, byte service = 0x00)
         {
             DstId = dstId;
             SrcId = srcId;
diff --git a/P25/lc/tsbk/IOSP_CALL_ALRT.cs b/P25/lc/tsbk/IOSP_CALL_ALRT.cs
index 58701ed..29d2e94 100644
--- a/P25/lc/tsbk/IOSP_CALL_ALRT.cs
+++ b/P25/lc/tsbk/IOSP_CALL_ALRT.cs
@@ -26,7 +26,7 @@ namespace fnecore.P25.LC.TSBK
         /// </summary>
         /// <param name="dstId"></param>
         /// <param name="srcId"></param>
-        public IOSP_CALL_ALRT(uint dstId, uint srcId)
+        public IOSP_CALL_ALRT(uint dstId = 0, uint srcId = 0)
         {
             DstId = dstId;
             SrcId = srcId;