diff --git a/sys/dev/if_ndis/if_ndis.c b/sys/dev/if_ndis/if_ndis.c
index 6c842a6..9d3e5b9 100644
--- a/sys/dev/if_ndis/if_ndis.c
+++ b/sys/dev/if_ndis/if_ndis.c
@@ -533,7 +533,8 @@ ndis_attach(dev)
 
 	sc = device_get_softc(dev);
 
-	KeInitializeSpinLock(&sc->ndis_spinlock);
+	mtx_init(&sc->ndis_mtx, device_get_nameunit(dev), MTX_NETWORK_LOCK,
+	    MTX_DEF);
 	KeInitializeSpinLock(&sc->ndis_rxlock);
 	InitializeListHead(&sc->ndis_shlist);
 	callout_init(&sc->ndis_stat_callout, CALLOUT_MPSAFE);
@@ -1644,7 +1645,6 @@ ndis_tick(xsc)
 	struct ndis_softc	*sc;
 
 	sc = xsc;
-	NDIS_LOCK(sc);
 
 	if (sc->ndis_hang_timer && --sc->ndis_hang_timer == 0) {
 		IoQueueWorkItem(sc->ndis_tickitem,
@@ -1654,6 +1654,7 @@ ndis_tick(xsc)
 	}
 
 	if (sc->ndis_tx_timer && --sc->ndis_tx_timer == 0) {
+		NDIS_LOCK(sc);
 		sc->ifp->if_oerrors++;
 		device_printf(sc->ndis_dev, "watchdog timeout\n");
 
@@ -1663,10 +1664,10 @@ ndis_tick(xsc)
 		IoQueueWorkItem(sc->ndis_startitem,
 		    (io_workitem_func)ndis_starttask_wrap,
 		    WORKQUEUE_CRITICAL, sc->ifp);
+		NDIS_UNLOCK(sc);
 	}
 
 	callout_reset(&sc->ndis_stat_callout, hz, ndis_tick, sc);
-	NDIS_UNLOCK(sc);
 }
 
 static void
diff --git a/sys/dev/if_ndis/if_ndisvar.h b/sys/dev/if_ndis/if_ndisvar.h
index d902d66..c339e16 100644
--- a/sys/dev/if_ndis/if_ndisvar.h
+++ b/sys/dev/if_ndis/if_ndisvar.h
@@ -129,7 +129,7 @@ struct ndis_softc {
 	struct resource		*ndis_res_cm;	/* common mem (pccard) */
 	struct resource_list	ndis_rl;
 	int			ndis_rescnt;
-	kspin_lock		ndis_spinlock;
+	struct mtx		ndis_mtx;
 	uint8_t			ndis_irql;
 	device_t		ndis_dev;
 	int			ndis_unit;
@@ -185,7 +185,5 @@ struct ndis_softc {
 	int			ndis_hang_timer;
 };
 
-#define NDIS_LOCK(_sc)		KeAcquireSpinLock(&(_sc)->ndis_spinlock, \
-				    &(_sc)->ndis_irql);
-#define NDIS_UNLOCK(_sc)	KeReleaseSpinLock(&(_sc)->ndis_spinlock, \
-				    (_sc)->ndis_irql);
+#define NDIS_LOCK(_sc)		mtx_lock(&(_sc)->ndis_mtx)
+#define NDIS_UNLOCK(_sc)	mtx_unlock(&(_sc)->ndis_mtx)