diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 021be39fe16e04b1ca9f172ec8206fceda2cdb5e..5b71962d0351d3a740be7d8a1d3e3aecef0a070d 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -2413,11 +2413,12 @@ static int mos7840_ioctl(struct usb_serial_port *port, struct file *file,
 	}
 
 	mos7840_port = mos7840_get_port_private(port);
-	tty = mos7840_port->port->tty;
 
 	if (mos7840_port == NULL)
 		return -1;
 
+	tty = mos7840_port->port->tty;
+
 	dbg("%s - port %d, cmd = 0x%x", __FUNCTION__, port->number, cmd);
 
 	switch (cmd) {