diff --git a/libs/freetdm/src/isdn/Q931.c b/libs/freetdm/src/isdn/Q931.c
index 191797d01d..f57365ecda 100644
--- a/libs/freetdm/src/isdn/Q931.c
+++ b/libs/freetdm/src/isdn/Q931.c
@@ -337,6 +337,10 @@ L3INT Q931Rx23(Q931_TrunkInfo_t *pTrunk, L3UCHAR * buf, L3INT Size)
     /* Starting Codeset */
 	m->codeset = Q931_CODESET_0;
 
+	if (m->ProtDisc != 8) {
+		return Q931E_UNKNOWN_MESSAGE;
+	}
+
     /* Call table proc to unpack codec message */
 	RetCode = Q931Umes[pTrunk->Dialect][m->MesType](pTrunk, Mes, (Q931mes_Generic *)pTrunk->L3Buf, Q931L4HeaderSpace + IOff , Size - Q931L4HeaderSpace - IOff + 1);
 
@@ -533,7 +537,7 @@ L3INT	Q931GetCallState(Q931_TrunkInfo_t *pTrunk, L3INT iCRV)
     L3INT x;
 	for(x=0; x < Q931MAXCALLPERTRUNK; x++)
 	{
-		if(!pTrunk->call[x].InUse)
+		if(pTrunk->call[x].InUse)
 		{
             if(pTrunk->call[x].CRV == iCRV)
             {
@@ -601,7 +605,7 @@ L3INT Q931FindCRV(Q931_TrunkInfo_t *pTrunk, L3INT crv, L3INT *callindex)
     L3INT x;
 	for(x=0; x < Q931MAXCALLPERTRUNK; x++)
 	{
-		if(!pTrunk->call[x].InUse)
+		if(pTrunk->call[x].InUse)
 		{
             if(pTrunk->call[x].CRV == crv)
             {
diff --git a/libs/freetdm/src/isdn/Q931StateTE.c b/libs/freetdm/src/isdn/Q931StateTE.c
index eb9c2a38fb..941d683710 100644
--- a/libs/freetdm/src/isdn/Q931StateTE.c
+++ b/libs/freetdm/src/isdn/Q931StateTE.c
@@ -793,15 +793,19 @@ L3INT Q931ProcRestartTE(Q931_TrunkInfo_t *pTrunk, L3UCHAR * buf, L3INT iFrom)
     L3INT ret=Q931E_NO_ERROR;
 	Q931mes_Header *pMes = (Q931mes_Header *)&buf[Q931L4HeaderSpace];
 
-	/* Find the call using CRV */
-	ret = Q931FindCRV(pTrunk, pMes->CRV, &callIndex);
-	if(ret != Q931E_NO_ERROR)
-		return ret;
+
+	if (pMes->CRV) {
+		/* Find the call using CRV */
+		ret = Q931FindCRV(pTrunk, pMes->CRV, &callIndex);
+		if(ret != Q931E_NO_ERROR)
+			return ret;
+
+		/* TODO - Set correct timer here */
+		Q931StartTimer(pTrunk, callIndex, 303);
+	}
 
 	/* TODO chack against state table for illegal or unexpected message here*/
 
-	/* TODO - Set correct timer here */
-    Q931StartTimer(pTrunk, callIndex, 303);
 	if(iFrom == 4)
 	{
 		/* TODO Add proc here*/
@@ -826,15 +830,17 @@ L3INT Q931ProcRestartAckTE(Q931_TrunkInfo_t *pTrunk, L3UCHAR * buf, L3INT iFrom)
     L3INT ret=Q931E_NO_ERROR;
 	Q931mes_Header *pMes = (Q931mes_Header *)&buf[Q931L4HeaderSpace];
 
-	/* Find the call using CRV */
-	ret = Q931FindCRV(pTrunk, pMes->CRV, &callIndex);
-	if(ret != Q931E_NO_ERROR)
-		return ret;
+	if (pMes->CRV) {
+		/* Find the call using CRV */
+		ret = Q931FindCRV(pTrunk, pMes->CRV, &callIndex);
+		if(ret != Q931E_NO_ERROR)
+			return ret;
+		/* TODO - Set correct timer here */
+		Q931StartTimer(pTrunk, callIndex, 303);
+	}
 
 	/* TODO chack against state table for illegal or unexpected message here*/
 
-	/* TODO - Set correct timer here */
-    Q931StartTimer(pTrunk, callIndex, 303);
 	if(iFrom == 4)
 	{
 		/* TODO Add proc here*/