diff --git a/deploy/nixos/hardware/upboard.nix b/deploy/nixos/hardware/upboard.nix
index 163b795..26e2842 100644
--- a/deploy/nixos/hardware/upboard.nix
+++ b/deploy/nixos/hardware/upboard.nix
@@ -24,9 +24,20 @@
       "usb_storage"
       "sd_mod"
       "sdhci_pci"
+      "sdhci-acpi" # UP Board sintra: eMMC controller is ACPI-enumerated, not PCI
+      "mmc_block" # creates /dev/mmcblk* block-device nodes
       "i915"
     ];
 
+    # Force-load the eMMC stack in stage 1 so root-by-label resolves before
+    # the kernel hands off to switch_root. Without this, initramfs panics
+    # with "An error occurred in stage 1 of the boot process" because
+    # /dev/disk/by-label/nixos never materialises in time.
+    initrd.kernelModules = [
+      "sdhci-acpi"
+      "mmc_block"
+    ];
+
     kernelModules = [
       "kvm-intel"
       "i2c-dev"
@@ -45,14 +56,19 @@
     ];
   };
 
-  # Disk layout: GPT with ESP + ext4 root (eMMC on UP Board)
+  # Disk layout: GPT with ESP + ext4 root (eMMC on UP Board).
+  # Labels match what make-disk-image.nix with partitionTableType="efi"
+  # produces — ESP for the FAT partition, nixos for the ext4 root. We
+  # previously expected `by-label/boot` here and had to manually
+  # `fatlabel` the partition post-flash; aligning the label avoids
+  # that hand-step on future re-flashes. (douro.nix already uses ESP.)
   fileSystems."/" = {
     device = "/dev/disk/by-label/nixos";
     fsType = "ext4";
   };
 
   fileSystems."/boot" = {
-    device = "/dev/disk/by-label/boot";
+    device = "/dev/disk/by-label/ESP";
     fsType = "vfat";
   };