diff --git a/lib/functions.bash b/lib/functions.bash
index c8b769a..7a025d4 100644
--- a/lib/functions.bash
+++ b/lib/functions.bash
@@ -8,7 +8,7 @@ function assert_root {
 }
 
 function assert_container {
-  cat /proc/self/cgroup | grep -qE'session-c[0-9]+\.scope'
+  [[ $(systemd-detect-virt -c) == lxc ]]
 }
 
 function assert_system_mode {