diff --git a/nixos/modules/virtualisation/azure-common.nix b/nixos/modules/virtualisation/azure-common.nix
index 8efa177e30d1..dc7853b95032 100644
--- a/nixos/modules/virtualisation/azure-common.nix
+++ b/nixos/modules/virtualisation/azure-common.nix
@@ -21,7 +21,11 @@ with lib;
   # way to select them anyway.
   boot.loader.grub.configurationLimit = 0;
 
-  fileSystems."/".device = "/dev/disk/by-label/nixos";
+  fileSystems."/" = {
+    device = "/dev/disk/by-label/nixos";
+    fsType = "ext4";
+    autoResize = true;
+  };
 
   # Allow root logins only using the SSH key that the user specified
   # at instance creation time, ping client connections to avoid timeouts