diff --git a/artiq/firmware/libboard/config.rs b/artiq/firmware/libboard/config.rs
index 665ccc462..443221d76 100644
--- a/artiq/firmware/libboard/config.rs
+++ b/artiq/firmware/libboard/config.rs
@@ -38,8 +38,8 @@ mod imp {
     use super::Error;
 
     // One flash sector immediately before the firmware.
-    const ADDR: usize = ::mem::FLASH_BOOT_ADDRESS - spiflash::PAGE_SIZE;
-    const SIZE: usize = spiflash::PAGE_SIZE;
+    const ADDR: usize = ::mem::FLASH_BOOT_ADDRESS - spiflash::SECTOR_SIZE;
+    const SIZE: usize = spiflash::SECTOR_SIZE;
 
     mod lock {
         use core::slice;
diff --git a/artiq/firmware/libboard/spiflash.rs b/artiq/firmware/libboard/spiflash.rs
index 2273185d5..3a4e7cb59 100644
--- a/artiq/firmware/libboard/spiflash.rs
+++ b/artiq/firmware/libboard/spiflash.rs
@@ -1,7 +1,8 @@
 use core::cmp;
 use csr;
 
-pub const PAGE_SIZE: usize = csr::CONFIG_SPIFLASH_PAGE_SIZE as usize;
+pub const SECTOR_SIZE: usize = csr::CONFIG_SPIFLASH_SECTOR_SIZE as usize;
+pub const PAGE_SIZE:   usize = csr::CONFIG_SPIFLASH_PAGE_SIZE   as usize;
 
 const PAGE_MASK: usize = PAGE_SIZE - 1;