diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 4157cc83518e700c17f92226b3a7780b41b5670e..cf9f41b8ab3f2f448cc858e1268a390ff3866814 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -5727,6 +5727,8 @@ const char *hangup_cause2sip(int cause)
 			return "502 Bad Gateway";
 		case AST_CAUSE_BEARERCAPABILITY_NOTAVAIL:	/* Can't find codec to connect to host */
 			return "488 Not Acceptable Here";
+		case AST_CAUSE_INTERWORKING:	/* Unspecified Interworking issues */
+			return "500 Network error";
 			
 		case AST_CAUSE_NOTDEFINED:
 		default: