diff --git a/dummyflasher.c b/dummyflasher.c
index ba40c6e..9ac83b6 100644
--- a/dummyflasher.c
+++ b/dummyflasher.c
@@ -112,7 +112,7 @@
 static uint16_t dummy_chip_readw(const struct flashctx *flash, const chipaddr addr);
 static uint32_t dummy_chip_readl(const struct flashctx *flash, const chipaddr addr);
 static void dummy_chip_readn(const struct flashctx *flash, uint8_t *buf, const chipaddr addr, size_t len);
-static bool dummy_spi_probe_opcode(struct flashctx *flash, uint8_t opcode);
+static bool dummy_spi_probe_opcode(const struct flashctx *flash, uint8_t opcode);
 
 static const struct spi_master spi_master_dummyflasher = {
 	.features	= SPI_MASTER_4BA,
@@ -1187,10 +1187,10 @@
 	return spi_write_chunked(flash, buf, start, len, data->spi_write_256_chunksize);
 }
 
-static bool dummy_spi_probe_opcode(struct flashctx *flash, uint8_t opcode)
+static bool dummy_spi_probe_opcode(const struct flashctx *flash, uint8_t opcode)
 {
 	size_t i;
-	struct emu_data *emu_data = flash->mst->spi.data;
+	const struct emu_data *emu_data = flash->mst->spi.data;
 	for (i = 0; i < emu_data->spi_blacklist_size; i++) {
 		if (emu_data->spi_blacklist[i] == opcode)
 			return false;
diff --git a/ichspi.c b/ichspi.c
index ee29288..afedaf2 100644
--- a/ichspi.c
+++ b/ichspi.c
@@ -1572,7 +1572,7 @@
 	return ret;
 }
 
-static bool ich_spi_probe_opcode(struct flashctx *flash, uint8_t opcode)
+static bool ich_spi_probe_opcode(const struct flashctx *flash, uint8_t opcode)
 {
 	return find_opcode(curopcodes, opcode) >= 0;
 }
diff --git a/include/programmer.h b/include/programmer.h
index b2c47a5..2a4a8f4 100644
--- a/include/programmer.h
+++ b/include/programmer.h
@@ -307,7 +307,7 @@
 	int (*write_256)(struct flashctx *flash, const uint8_t *buf, unsigned int start, unsigned int len);
 	int (*write_aai)(struct flashctx *flash, const uint8_t *buf, unsigned int start, unsigned int len);
 	int (*shutdown)(void *data);
-	bool (*probe_opcode)(struct flashctx *flash, uint8_t opcode);
+	bool (*probe_opcode)(const struct flashctx *flash, uint8_t opcode);
 	void *data;
 };
 
@@ -317,7 +317,7 @@
 int default_spi_read(struct flashctx *flash, uint8_t *buf, unsigned int start, unsigned int len);
 int default_spi_write_256(struct flashctx *flash, const uint8_t *buf, unsigned int start, unsigned int len);
 int default_spi_write_aai(struct flashctx *flash, const uint8_t *buf, unsigned int start, unsigned int len);
-bool default_spi_probe_opcode(struct flashctx *flash, uint8_t opcode);
+bool default_spi_probe_opcode(const struct flashctx *flash, uint8_t opcode);
 int register_spi_master(const struct spi_master *mst, void *data);
 
 /* The following enum is needed by ich_descriptor_tool and ich* code as well as in chipset_enable.c. */
diff --git a/spi.c b/spi.c
index 98b6b12..bb6f976 100644
--- a/spi.c
+++ b/spi.c
@@ -131,7 +131,7 @@
 	return default_spi_write_aai(flash, buf, start, len);
 }
 
-bool default_spi_probe_opcode(struct flashctx *flash, uint8_t opcode)
+bool default_spi_probe_opcode(const struct flashctx *flash, uint8_t opcode)
 {
 	return true;
 }