diff --git a/src/drivers/net/ipoib.c b/src/drivers/net/ipoib.c
index 7ecb2c5dd..6552d764e 100644
--- a/src/drivers/net/ipoib.c
+++ b/src/drivers/net/ipoib.c
@@ -791,7 +791,8 @@ static void ipoib_link_state_changed ( struct ib_device *ibdev ) {
 	int rc;
 
 	/* Leave existing broadcast group */
-	ipoib_leave_broadcast_group ( ipoib );
+	if ( ipoib->qp )
+		ipoib_leave_broadcast_group ( ipoib );
 
 	/* Update MAC address based on potentially-new GID prefix */
 	memcpy ( &ipoib->mac.gid.s.prefix, &ibdev->gid.s.prefix,
@@ -806,7 +807,7 @@ static void ipoib_link_state_changed ( struct ib_device *ibdev ) {
 	netdev_link_err ( netdev, ( rc ? rc : -EINPROGRESS_JOINING ) );
 
 	/* Join new broadcast group */
-	if ( ib_is_open ( ibdev ) && ib_link_ok ( ibdev ) &&
+	if ( ib_is_open ( ibdev ) && ib_link_ok ( ibdev ) && ipoib->qp &&
 	     ( ( rc = ipoib_join_broadcast_group ( ipoib ) ) != 0 ) ) {
 		DBGC ( ipoib, "IPoIB %p could not rejoin broadcast group: "
 		       "%s\n", ipoib, strerror ( rc ) );
@@ -894,7 +895,9 @@ static void ipoib_close ( struct net_device *netdev ) {
 
 	/* Tear down the queues */
 	ib_destroy_qp ( ibdev, ipoib->qp );
+	ipoib->qp = NULL;
 	ib_destroy_cq ( ibdev, ipoib->cq );
+	ipoib->cq = NULL;
 
 	/* Close IB device */
 	ib_close ( ibdev );
diff --git a/src/net/infiniband.c b/src/net/infiniband.c
index 8ba031f1d..2e3d76d54 100644
--- a/src/net/infiniband.c
+++ b/src/net/infiniband.c
@@ -718,6 +718,9 @@ int ib_mcast_attach ( struct ib_device *ibdev, struct ib_queue_pair *qp,
 	struct ib_multicast_gid *mgid;
 	int rc;
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Add to software multicast GID list */
 	mgid = zalloc ( sizeof ( *mgid ) );
 	if ( ! mgid ) {
@@ -751,6 +754,9 @@ void ib_mcast_detach ( struct ib_device *ibdev, struct ib_queue_pair *qp,
 		       union ib_gid *gid ) {
 	struct ib_multicast_gid *mgid;
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Remove from hardware multicast GID list */
 	ibdev->op->mcast_detach ( ibdev, qp, gid );
 
diff --git a/src/net/infiniband/ib_mcast.c b/src/net/infiniband/ib_mcast.c
index 02369269f..fc4ff7f0a 100644
--- a/src/net/infiniband/ib_mcast.c
+++ b/src/net/infiniband/ib_mcast.c
@@ -150,6 +150,9 @@ int ib_mcast_join ( struct ib_device *ibdev, struct ib_queue_pair *qp,
 	DBGC ( ibdev, "IBDEV %p QPN %lx joining " IB_GID_FMT "\n",
 	       ibdev, qp->qpn, IB_GID_ARGS ( gid ) );
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Initialise structure */
 	membership->qp = qp;
 	memcpy ( &membership->gid, gid, sizeof ( membership->gid ) );
@@ -199,6 +202,9 @@ void ib_mcast_leave ( struct ib_device *ibdev, struct ib_queue_pair *qp,
 	DBGC ( ibdev, "IBDEV %p QPN %lx leaving " IB_GID_FMT "\n",
 	       ibdev, qp->qpn, IB_GID_ARGS ( gid ) );
 
+	/* Sanity check */
+	assert ( qp != NULL );
+
 	/* Detach from multicast GID */
 	ib_mcast_detach ( ibdev, qp, &membership->gid );