diff --git a/bitbang_spi.c b/bitbang_spi.c
index 850ca32..91f48a9 100644
--- a/bitbang_spi.c
+++ b/bitbang_spi.c
@@ -21,6 +21,10 @@
 #include "programmer.h"
 #include "spi.h"
 
+struct bitbang_spi_master_data {
+	const struct bitbang_spi_master *mst;
+};
+
 /* Note that CS# is active low, so val=0 means the chip is active. */
 static void bitbang_spi_set_cs(const struct bitbang_spi_master * const master, int val)
 {
@@ -68,6 +72,7 @@
 				    unsigned int writecnt, unsigned int readcnt,
 				    const unsigned char *writearr,
 				    unsigned char *readarr);
+static int bitbang_spi_shutdown(void *data);
 
 static const struct spi_master spi_master_bitbang = {
 	.features	= SPI_MASTER_4BA,
@@ -77,16 +82,16 @@
 	.multicommand	= default_spi_send_multicommand,
 	.read		= default_spi_read,
 	.write_256	= default_spi_write_256,
+	.shutdown	= bitbang_spi_shutdown,
 	.probe_opcode	= default_spi_probe_opcode,
 };
 
-#if 0 // until it is needed
-static int bitbang_spi_shutdown(const struct bitbang_spi_master *master)
+static int bitbang_spi_shutdown(void *data)
 {
 	/* FIXME: Run bitbang_spi_release_bus here or per command? */
+	free(data);
 	return 0;
 }
-#endif
 
 int register_spi_bitbang_master(const struct bitbang_spi_master *master)
 {
@@ -101,9 +106,14 @@
 		return ERROR_FLASHROM_BUG;
 	}
 
-	/* Cast away `const`, but local code must ensure it's still treated as such. */
-	mst.data = (struct bitbang_spi_master *)master;
-	register_spi_master(&mst, NULL);
+	struct bitbang_spi_master_data *data = calloc(1, sizeof(struct bitbang_spi_master_data));
+	if (!data) {
+		msg_perr("Out of memory!\n");
+		return ERROR_OOM;
+	}
+
+	data->mst = master;
+	register_spi_master(&mst, data);
 
 	/* Only mess with the bus if we're sure nobody else uses it. */
 	bitbang_spi_request_bus(master);
@@ -152,7 +162,8 @@
 				    unsigned char *readarr)
 {
 	unsigned int i;
-	const struct bitbang_spi_master *master = flash->mst->spi.data;
+	const struct bitbang_spi_master_data *data = flash->mst->spi.data;
+	const struct bitbang_spi_master *master = data->mst;
 
 	/* FIXME: Run bitbang_spi_request_bus here or in programmer init?
 	 * Requesting and releasing the SPI bus is handled in here to allow the