diff --git a/dmx_usb.c b/dmx_usb.c
index 4e3372d..7dfb814 100644
--- a/dmx_usb.c
+++ b/dmx_usb.c
@@ -97,7 +97,7 @@ struct dmx_usb_device {
 
 
 /* prevent races between open() and disconnect() */
-	static DEFINE_SEMAPHORE(disconnect_sem);
+	static DEFINE_SEMAPHORE(disconnect_sem, 1);
 
 /* local function prototypes */
 static ssize_t dmx_usb_write	(struct file *file, const char *buffer, size_t count, loff_t *ppos);