diff --git a/nixos/modules/installer/cd-dvd/iso-image.nix b/nixos/modules/installer/cd-dvd/iso-image.nix
index 324b38070e47..5910bfc05ac2 100644
--- a/nixos/modules/installer/cd-dvd/iso-image.nix
+++ b/nixos/modules/installer/cd-dvd/iso-image.nix
@@ -415,7 +415,24 @@ let
       echo "Image size: $image_size"
       truncate --size=$image_size "$out"
       faketime "2000-01-01 00:00:00" mkfs.vfat -i 12345678 -n EFIBOOT "$out"
-      mcopy -psvm -i "$out" ./EFI ./boot ::
+
+      # Force a fixed order in mcopy for better determinism, and avoid file globbing
+      for d in $(find EFI -type d | sort); do
+        faketime "2000-01-01 00:00:00" mmd -i "$out" "::/$d"
+      done
+
+      for d in $(find boot -type d | sort); do
+        faketime "2000-01-01 00:00:00" mmd -i "$out" "::/$d"
+      done
+
+      for f in $(find EFI -type f | sort); do
+        mcopy -pvm -i "$out" "$f" "::/$f"
+      done
+
+      for f in $(find boot -type f | sort); do
+        mcopy -pvm -i "$out" "$f" "::/$f"
+      done
+
       # Verify the FAT partition.
       fsck.vfat -vn "$out"
     ''; # */