diff --git a/lib/functions.bash b/lib/functions.bash
index 7a025d4..7f14795 100644
--- a/lib/functions.bash
+++ b/lib/functions.bash
@@ -1,5 +1,9 @@
 ## library of useful functions, usually prefixed with '_'
 
+function sudo_root {
+  [[ "$UID" -ne 0 ]] && sudo -vp 'SUDO privilege required: '
+}
+
 ## ASSERT Functions
 
 function assert_root {
@@ -16,7 +20,7 @@ function assert_system_mode {
     >&2 echo "ERROR: development mode: $(realpath "$MIAOU_BASH_DIR")" &&
     return 3
 
-  assert_container && [[ ! -w $MIAOU_BASH_DIR ]] &&
+  assert_container && ! sudo test -w "$MIAOU_BASH_DIR" &&
     >&2 echo "ERROR: hosted mode" &&
     return 4
 
diff --git a/lib/self-upgrade.bash b/lib/self-upgrade.bash
index f5767fb..b0baaa3 100644
--- a/lib/self-upgrade.bash
+++ b/lib/self-upgrade.bash
@@ -22,6 +22,7 @@ function self_upgrade {
 # MAIN
 
 source "$MIAOU_BASH_DIR"/lib/functions.bash
+sudo_root
 assert_system_mode
 
 current=$(miaou-bash --version)