diff --git a/src/shared/gatt-client.c b/src/shared/gatt-client.c
index 729bd87..056f812 100644
--- a/src/shared/gatt-client.c
+++ b/src/shared/gatt-client.c
unsigned int bt_gatt_client_prepare_write(struct bt_gatt_client *client,
unsigned int id, uint16_t value_handle,
- uint16_t offset, uint8_t *value,
+ uint16_t offset, const uint8_t *value,
uint16_t length,
bt_gatt_client_write_long_callback_t callback,
void *user_data,
diff --git a/src/shared/gatt-client.h b/src/shared/gatt-client.h
index 8e5e0f5..b816cc4 100644
--- a/src/shared/gatt-client.h
+++ b/src/shared/gatt-client.h
unsigned int bt_gatt_client_prepare_write(struct bt_gatt_client *client,
unsigned int id,
uint16_t value_handle, uint16_t offset,
- uint8_t *value, uint16_t length,
+ const uint8_t *value, uint16_t length,
bt_gatt_client_write_long_callback_t callback,
void *user_data,
bt_gatt_client_destroy_func_t destroy);