diff --git a/libs/freetdm/src/include/zap_types.h b/libs/freetdm/src/include/zap_types.h
index 5833e6401a..673734ca1c 100644
--- a/libs/freetdm/src/include/zap_types.h
+++ b/libs/freetdm/src/include/zap_types.h
@@ -195,9 +195,11 @@ typedef enum {
 	/* The channel signaling link is suspended (MFC-R2 bit pattern blocked, ss7 blocked?) */
 	ZAP_SIG_STATE_SUSPENDED,
 	/* The channel signaling link is ready and calls can be placed */
-	ZAP_SIG_STATE_UP
+	ZAP_SIG_STATE_UP,
+	/* Invalid status */
+	ZAP_SIG_STATE_INVALID
 } zap_channel_sig_status_t;
-#define SIGSTATUS_STRINGS "DOWN", "SUSPENDED", "UP"
+#define SIGSTATUS_STRINGS "DOWN", "SUSPENDED", "UP", "INVALID"
 ZAP_STR2ENUM_P(zap_str2zap_channel_sig_status, zap_sig_status2str, zap_channel_sig_status_t)
 
 typedef enum {
diff --git a/libs/freetdm/src/zap_io.c b/libs/freetdm/src/zap_io.c
index 51c7a2e813..8f88695893 100644
--- a/libs/freetdm/src/zap_io.c
+++ b/libs/freetdm/src/zap_io.c
@@ -114,6 +114,8 @@ ZAP_STR2ENUM(zap_str2zap_mdmf_type, zap_mdmf_type2str, zap_mdmf_type_t, MDMF_TYP
 ZAP_ENUM_NAMES(CHAN_TYPE_NAMES, CHAN_TYPE_STRINGS)
 ZAP_STR2ENUM(zap_str2zap_chan_type, zap_chan_type2str, zap_chan_type_t, CHAN_TYPE_NAMES, ZAP_CHAN_TYPE_COUNT)
 
+ZAP_ENUM_NAMES(CHAN_SIG_STATUS_NAMES, SIGSTATUS_STRINGS)
+ZAP_STR2ENUM(zap_str2zap_channel_sig_status, zap_sig_status2str, zap_channel_sig_status_t, CHAN_SIG_STATUS_NAMES, ZAP_SIG_STATE_INVALID)
 
 static const char *cut_path(const char *in)
 {