diff --git a/nixos/modules/system/boot/systemd/initrd.nix b/nixos/modules/system/boot/systemd/initrd.nix
index e4f61db0cd02..06359f273846 100644
--- a/nixos/modules/system/boot/systemd/initrd.nix
+++ b/nixos/modules/system/boot/systemd/initrd.nix
@@ -392,7 +392,10 @@ in {
 
     boot.kernelParams = [
       "root=${config.boot.initrd.systemd.root}"
-    ] ++ lib.optional (config.boot.resumeDevice != "") "resume=${config.boot.resumeDevice}";
+    ] ++ lib.optional (config.boot.resumeDevice != "") "resume=${config.boot.resumeDevice}"
+      # `systemd` mounts root in initrd as read-only unless "rw" is on the kernel command line.
+      # For NixOS activation to succeed, we need to have root writable in initrd.
+      ++ lib.optional (config.boot.initrd.systemd.root == "gpt-auto") "rw";
 
     boot.initrd.systemd = {
       initrdBin = [pkgs.bash pkgs.coreutils cfg.package.kmod cfg.package];