diff --git a/serprog.c b/serprog.c
index 37a9db4..1befce1 100644
--- a/serprog.c
+++ b/serprog.c
@@ -295,7 +295,7 @@
 	return 0;
 }
 
-static int serprog_spi_send_command(struct flashctx *flash,
+static int serprog_spi_send_command(const struct flashctx *flash,
 				    unsigned int writecnt, unsigned int readcnt,
 				    const unsigned char *writearr,
 				    unsigned char *readarr);
@@ -894,7 +894,7 @@
 	sp_prev_was_write = 0;
 }
 
-static int serprog_spi_send_command(struct flashctx *flash,
+static int serprog_spi_send_command(const struct flashctx *flash,
 				    unsigned int writecnt, unsigned int readcnt,
 				    const unsigned char *writearr,
 				    unsigned char *readarr)