diff --git a/software/include/base/spiflash.h b/software/include/base/spiflash.h
index ce5a1d9bb..a4ff495ab 100644
--- a/software/include/base/spiflash.h
+++ b/software/include/base/spiflash.h
@@ -1,8 +1,8 @@
 #ifndef __SPIFLASH_H
 #define __SPIFLASH_H
 
-void write_to_flash_page(unsigned int addr, unsigned char *c, unsigned int len);
+void write_to_flash_page(unsigned int addr, const unsigned char *c, unsigned int len);
 void erase_flash_sector(unsigned int addr);
-void write_to_flash(unsigned int addr, unsigned char *c, unsigned int len);
+void write_to_flash(unsigned int addr, const unsigned char *c, unsigned int len);
 
 #endif /* __SPIFLASH_H */
diff --git a/software/libbase/spiflash.c b/software/libbase/spiflash.c
index 529fd47b4..31d56a106 100644
--- a/software/libbase/spiflash.c
+++ b/software/libbase/spiflash.c
@@ -89,7 +89,7 @@ void erase_flash_sector(unsigned int addr)
     spiflash_bitbang_en_write(0);
 }
 
-void write_to_flash_page(unsigned int addr, unsigned char *c, unsigned int len)
+void write_to_flash_page(unsigned int addr, const unsigned char *c, unsigned int len)
 {
     unsigned int i;
 
@@ -117,7 +117,7 @@ void write_to_flash_page(unsigned int addr, unsigned char *c, unsigned int len)
 
 #define SPIFLASH_PAGE_MASK (SPIFLASH_PAGE_SIZE - 1)
 
-void write_to_flash(unsigned int addr, unsigned char *c, unsigned int len)
+void write_to_flash(unsigned int addr, const unsigned char *c, unsigned int len)
 {
    unsigned int written = 0;