diff --git a/ft2232_spi.c b/ft2232_spi.c
index 5bdc2a7..d63aa8d 100644
--- a/ft2232_spi.c
+++ b/ft2232_spi.c
@@ -148,7 +148,7 @@
 	return 0;
 }
 
-static int ft2232_spi_send_command(struct flashctx *flash,
+static int ft2232_spi_send_command(const struct flashctx *flash,
 				   unsigned int writecnt, unsigned int readcnt,
 				   const unsigned char *writearr,
 				   unsigned char *readarr);
@@ -447,7 +447,7 @@
 }
 
 /* Returns 0 upon success, a negative number upon errors. */
-static int ft2232_spi_send_command(struct flashctx *flash,
+static int ft2232_spi_send_command(const struct flashctx *flash,
 				   unsigned int writecnt, unsigned int readcnt,
 				   const unsigned char *writearr,
 				   unsigned char *readarr)