diff --git a/common/usb_storage.c b/common/usb_storage.c
index 613c4f0..1e6cd6a 100644
--- a/common/usb_storage.c
+++ b/common/usb_storage.c
@@ -70,7 +70,7 @@
 /* direction table -- this indicates the direction of the data
  * transfer for each command code -- a 1 indicates input
  */
-unsigned char us_direction[256/8] = {
+static const unsigned char us_direction[256/8] = {
 	0x28, 0x81, 0x14, 0x14, 0x20, 0x01, 0x90, 0x77,
 	0x0C, 0x20, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00,
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01,