diff --git a/wbsio_spi.c b/wbsio_spi.c
index f4f6af9..1674825 100644
--- a/wbsio_spi.c
+++ b/wbsio_spi.c
@@ -57,7 +57,7 @@
 	return flashport;
 }
 
-static int wbsio_spi_send_command(struct flashctx *flash, unsigned int writecnt,
+static int wbsio_spi_send_command(const struct flashctx *flash, unsigned int writecnt,
 				  unsigned int readcnt,
 				  const unsigned char *writearr,
 				  unsigned char *readarr);
@@ -110,7 +110,7 @@
  * Would one more byte of RAM in the chip (to get all 24 bits) really make
  * such a big difference?
  */
-static int wbsio_spi_send_command(struct flashctx *flash, unsigned int writecnt,
+static int wbsio_spi_send_command(const struct flashctx *flash, unsigned int writecnt,
 				  unsigned int readcnt,
 				  const unsigned char *writearr,
 				  unsigned char *readarr)