diff --git a/usb_serial.c b/usb_serial.c
index 13626e1..9893a35 100644
--- a/usb_serial.c
+++ b/usb_serial.c
@@ -152,7 +152,7 @@ static const uint8_t PROGMEM endpoint_config_table[] = {
 // in here should only be done by those who've read chapter 9 of the USB
 // spec and relevant portions of any USB class specifications!
 
-static uint8_t PROGMEM device_descriptor[] = {
+static const uint8_t PROGMEM device_descriptor[] = {
 	18,					// bLength
 	1,					// bDescriptorType
 	0x00, 0x02,				// bcdUSB
@@ -170,7 +170,7 @@ static uint8_t PROGMEM device_descriptor[] = {
 };
 
 #define CONFIG1_DESC_SIZE (9+9+5+5+4+5+7+9+7+7)
-static uint8_t PROGMEM config1_descriptor[CONFIG1_DESC_SIZE] = {
+static const uint8_t PROGMEM config1_descriptor[CONFIG1_DESC_SIZE] = {
 	// configuration descriptor, USB spec 9.6.3, page 264-266, Table 9-10
 	9, 					// bLength;
 	2,					// bDescriptorType;
@@ -254,22 +254,22 @@ struct usb_string_descriptor_struct {
 	uint8_t bDescriptorType;
 	int16_t wString[];
 };
-static struct usb_string_descriptor_struct PROGMEM string0 = {
+static const struct usb_string_descriptor_struct PROGMEM string0 = {
 	4,
 	3,
 	{0x0409}
 };
-static struct usb_string_descriptor_struct PROGMEM string1 = {
+static const struct usb_string_descriptor_struct PROGMEM string1 = {
 	sizeof(STR_MANUFACTURER),
 	3,
 	STR_MANUFACTURER
 };
-static struct usb_string_descriptor_struct PROGMEM string2 = {
+static const struct usb_string_descriptor_struct PROGMEM string2 = {
 	sizeof(STR_PRODUCT),
 	3,
 	STR_PRODUCT
 };
-static struct usb_string_descriptor_struct PROGMEM string3 = {
+static const struct usb_string_descriptor_struct PROGMEM string3 = {
 	sizeof(STR_SERIAL_NUMBER),
 	3,
 	STR_SERIAL_NUMBER
@@ -277,7 +277,7 @@ static struct usb_string_descriptor_struct PROGMEM string3 = {
 
 // This table defines which descriptor data is sent for each specific
 // request from the host (in wValue and wIndex).
-static struct descriptor_list_struct {
+static const struct descriptor_list_struct {
 	uint16_t	wValue;
 	uint16_t	wIndex;
 	const uint8_t	*addr;