diff --git a/metropolis/node/core/localstorage/directory_root.go b/metropolis/node/core/localstorage/directory_root.go
index c3a49cb..44af268 100644
--- a/metropolis/node/core/localstorage/directory_root.go
+++ b/metropolis/node/core/localstorage/directory_root.go
@@ -39,7 +39,7 @@
 		return fmt.Errorf("MakeBlockDevices: %w", err)
 	}
 
-	if err := unix.Mount(crypt.ESPDevicePath, r.ESP.FullPath(), "vfat", unix.MS_NOEXEC|unix.MS_NODEV|unix.MS_SYNC, ""); err != nil {
+	if err := unix.Mount(crypt.ESPDevicePath, r.ESP.FullPath(), "vfat", unix.MS_NOEXEC|unix.MS_NODEV|unix.MS_SYNCHRONOUS, ""); err != nil {
 		return fmt.Errorf("mounting ESP partition: %w", err)
 	}