diff --git a/virt-card/device-sim.c b/virt-card/device-sim.c
index ea8ad11f..7d63a9e3 100644
--- a/virt-card/device-sim.c
+++ b/virt-card/device-sim.c
@@ -70,7 +70,7 @@ uint32_t device_get_tick(void) {
 void device_disable_irq(void) {}
 void device_enable_irq(void) {}
 void device_set_timeout(void (*callback)(void), uint16_t timeout) {}
-void fm_write_eeprom(uint16_t addr, uint8_t *buf, uint8_t len) { return; }
+void fm_write_eeprom(uint16_t addr, const uint8_t *buf, uint8_t len) { return; }
 
 int device_atomic_compare_and_swap(volatile uint32_t *var, uint32_t expect, uint32_t update) {
   if (*var == expect) {