Index: src/request.c
--- src/request.c.orig
+++ src/request.c
@@ -194,6 +194,8 @@ void sendGroupSpecificMemberQuery(void *argument) {
     // Loop through all downstream interfaces
     for ( Ix = 0; (Dp = getIfByIx(Ix)); Ix++ ) {
         if ( Dp->InAdr.s_addr && ! (Dp->Flags & IFF_LOOPBACK) ) {
+            if (config_getinterface(Dp->Name) == NULL)
+                continue;
             if(Dp->state == IF_STATE_DOWNSTREAM) {
                 // Is that interface used in the group?
                 if (interfaceInRoute(gvDesc->group ,Dp->index)) {