diff --git a/src/machine/machine.h b/src/machine/machine.h
index 8f1a044f7a..4bdb049c5f 100644
--- a/src/machine/machine.h
+++ b/src/machine/machine.h
@@ -45,6 +45,8 @@ typedef struct Machine {
 
         char *state_file;
         char *service;
+        /* Note that the root directory is accepted as-is from the caller, including unprivileged users, so
+         * do not use it for anything but informational purposes. */
         char *root_directory;
 
         char *unit;