diff --git a/ni845x_spi.c b/ni845x_spi.c
index 92184ff..73b236e 100644
--- a/ni845x_spi.c
+++ b/ni845x_spi.c
@@ -583,7 +583,7 @@
 	return 0;
 }
 
-static int ni845x_spi_transmit(struct flashctx *flash,
+static int ni845x_spi_transmit(const struct flashctx *flash,
 			       unsigned int write_cnt,
 			       unsigned int read_cnt,
 			       const unsigned char *write_arr,