diff --git a/jedec.h b/jedec.h
index 1751b29..4a86913 100644
--- a/jedec.h
+++ b/jedec.h
@@ -5,7 +5,7 @@
 extern int erase_chip_jedec(struct flashchip *flash);
 extern int write_jedec(struct flashchip *flash, unsigned char *buf);
 extern int erase_sector_jedec(volatile char *bios, unsigned int page);
-extern int write_sector_jedec(volatile char *bios,
+extern int write_sector_jedec(volatile unsigned char *bios,
 			      unsigned char *src,
 			      volatile unsigned char *dst,
 			      unsigned int page_size);