diff --git a/buspirate_spi.c b/buspirate_spi.c
index 826bd84..fdfc0e4 100644
--- a/buspirate_spi.c
+++ b/buspirate_spi.c
@@ -128,9 +128,9 @@
 	return ret;
 }
 
-static int buspirate_spi_send_command_v1(struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
+static int buspirate_spi_send_command_v1(const struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
 					 const unsigned char *writearr, unsigned char *readarr);
-static int buspirate_spi_send_command_v2(struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
+static int buspirate_spi_send_command_v2(const struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
 					 const unsigned char *writearr, unsigned char *readarr);
 
 static struct spi_master spi_master_buspirate = {
@@ -572,7 +572,7 @@
 	return 0;
 }
 
-static int buspirate_spi_send_command_v1(struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
+static int buspirate_spi_send_command_v1(const struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
 					 const unsigned char *writearr, unsigned char *readarr)
 {
 	unsigned int i = 0;
@@ -625,7 +625,7 @@
 	return ret;
 }
 
-static int buspirate_spi_send_command_v2(struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
+static int buspirate_spi_send_command_v2(const struct flashctx *flash, unsigned int writecnt, unsigned int readcnt,
 					 const unsigned char *writearr, unsigned char *readarr)
 {
 	int i = 0, ret = 0;