diff --git a/hw/ppc/mac_newworld.c b/hw/ppc/mac_newworld.c
index a365bf92235d717d229f2ec4e77af56149e8b9a3..0f3e34122a1786c59fbcc3805c560da75abe72e4 100644
--- a/hw/ppc/mac_newworld.c
+++ b/hw/ppc/mac_newworld.c
@@ -119,7 +119,7 @@ static const MemoryRegionOps unin_ops = {
 static void fw_cfg_boot_set(void *opaque, const char *boot_device,
                             Error **errp)
 {
-    fw_cfg_add_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
+    fw_cfg_modify_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
 }
 
 static uint64_t translate_kernel_address(void *opaque, uint64_t addr)
diff --git a/hw/ppc/mac_oldworld.c b/hw/ppc/mac_oldworld.c
index f26133dedd152cb042163c5c8d007e06ad37dd70..99879dd2d5808dc810cd243aee479e5d41e1cb8a 100644
--- a/hw/ppc/mac_oldworld.c
+++ b/hw/ppc/mac_oldworld.c
@@ -52,7 +52,7 @@
 static void fw_cfg_boot_set(void *opaque, const char *boot_device,
                             Error **errp)
 {
-    fw_cfg_add_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
+    fw_cfg_modify_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
 }
 
 static uint64_t translate_kernel_address(void *opaque, uint64_t addr)
diff --git a/hw/sparc/sun4m.c b/hw/sparc/sun4m.c
index 8a3599c403c01b0b499021ca3d2b2b46405573ca..68ac4d8bba1173c8185f6410ddf19f7189544dcf 100644
--- a/hw/sparc/sun4m.c
+++ b/hw/sparc/sun4m.c
@@ -124,7 +124,7 @@ void DMA_register_channel (int nchan,
 static void fw_cfg_boot_set(void *opaque, const char *boot_device,
                             Error **errp)
 {
-    fw_cfg_add_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
+    fw_cfg_modify_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
 }
 
 static void nvram_init(Nvram *nvram, uint8_t *macaddr,
diff --git a/hw/sparc64/sun4u.c b/hw/sparc64/sun4u.c
index 6f34e879352955b64023a3f5bbc65e5bd984cd6f..30cfa0e0a0d5de23c6b99e10525c8cc3b22477f8 100644
--- a/hw/sparc64/sun4u.c
+++ b/hw/sparc64/sun4u.c
@@ -127,7 +127,7 @@ void DMA_register_channel (int nchan,
 static void fw_cfg_boot_set(void *opaque, const char *boot_device,
                             Error **errp)
 {
-    fw_cfg_add_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
+    fw_cfg_modify_i16(opaque, FW_CFG_BOOT_DEVICE, boot_device[0]);
 }
 
 static int sun4u_NVRAM_set_params(Nvram *nvram, uint16_t NVRAM_size,