diff --git a/sys/dev/mfi/mfi.c b/sys/dev/mfi/mfi.c
index b5b2eb9d5a83..3a96d9642823 100644
--- a/sys/dev/mfi/mfi.c
+++ b/sys/dev/mfi/mfi.c
@@ -1779,14 +1779,20 @@ static int
 mfi_open(struct cdev *dev, int flags, int fmt, d_thread_t *td)
 {
 	struct mfi_softc *sc;
+	int error;
 
 	sc = dev->si_drv1;
 
 	mtx_lock(&sc->mfi_io_lock);
-	sc->mfi_flags |= MFI_FLAGS_OPEN;
+	if (sc->mfi_detaching)
+		error = ENXIO;
+	else {
+		sc->mfi_flags |= MFI_FLAGS_OPEN;
+		error = 0;
+	}
 	mtx_unlock(&sc->mfi_io_lock);
 
-	return (0);
+	return (error);
 }
 
 static int
diff --git a/sys/dev/mfi/mfi_pci.c b/sys/dev/mfi/mfi_pci.c
index a335bd21eef0..45e831140180 100644
--- a/sys/dev/mfi/mfi_pci.c
+++ b/sys/dev/mfi/mfi_pci.c
@@ -204,6 +204,7 @@ mfi_pci_detach(device_t dev)
 	mtx_lock(&sc->mfi_io_lock);
 	if ((sc->mfi_flags & MFI_FLAGS_OPEN) != 0) {
 		mtx_unlock(&sc->mfi_io_lock);
+		sx_xunlock(&sc->mfi_config_lock);
 		return (EBUSY);
 	}
 	sc->mfi_detaching = 1;