diff --git a/firmware/usb.c b/firmware/usb.c
index 2f277ac200..8d61f2e60c 100644
--- a/firmware/usb.c
+++ b/firmware/usb.c
@@ -331,6 +331,7 @@ static inline void usb_slave_mode(bool on)
         if(rc)
             panicf("storage: %d",rc);
 
+        sleep(HZ/10);
         rc = disk_mount_all();
         if(rc <= 0) /* no partition */
             panicf("mount: %d",rc);