diff --git a/man/systemd-machine-id-setup.xml b/man/systemd-machine-id-setup.xml
index b879b40b99..62630fbcab 100644
--- a/man/systemd-machine-id-setup.xml
+++ b/man/systemd-machine-id-setup.xml
@@ -97,11 +97,12 @@
 
                 <variablelist>
                         <varlistentry>
-                                <term><option>--root=ROOT</option></term>
+                                <term><option>--root=<replaceable>root</replaceable></option></term>
                                 <listitem><para>Takes a directory path
                                 as an argument. All paths will be
-                                prefixed with the given alternate ROOT
-                                path, including config search paths.
+                                prefixed with the given alternate
+                                <replaceable>root</replaceable> path,
+                                including config search paths.
                                 </para></listitem>
                         </varlistentry>
                         <xi:include href="standard-options.xml" xpointer="help" />
diff --git a/src/core/machine-id-setup.c b/src/core/machine-id-setup.c
index f3b1b318e1..43720d6289 100644
--- a/src/core/machine-id-setup.c
+++ b/src/core/machine-id-setup.c
@@ -36,6 +36,7 @@
 #include "log.h"
 #include "virt.h"
 #include "fileio.h"
+#include "path-util.h"
 
 static int shorten_uuid(char destination[36], const char *source) {
         unsigned i, j;
@@ -160,14 +161,13 @@ int machine_id_setup(const char *root) {
         bool writable = false;
         struct stat st;
         char id[34]; /* 32 + \n + \0 */
-        _cleanup_free_ char *etc_machine_id = NULL;
-        _cleanup_free_ char *run_machine_id = NULL;
+        char *etc_machine_id, *run_machine_id;
 
-        if (asprintf(&etc_machine_id, "%s/etc/machine-id", root) < 0)
-                return log_oom();
+        etc_machine_id = strappenda(root, "/etc/machine-id");
+        path_kill_slashes(etc_machine_id);
 
-        if (asprintf(&run_machine_id, "%s/run/machine-id", root) < 0)
-                return log_oom();
+        run_machine_id = strappenda(root, "/run/machine-id");
+        path_kill_slashes(run_machine_id);
 
         RUN_WITH_UMASK(0000) {
                 /* We create this 0444, to indicate that this isn't really
diff --git a/src/machine-id-setup/machine-id-setup-main.c b/src/machine-id-setup/machine-id-setup-main.c
index a67d436dbd..1c933ce600 100644
--- a/src/machine-id-setup/machine-id-setup-main.c
+++ b/src/machine-id-setup/machine-id-setup-main.c
@@ -37,7 +37,7 @@ static int help(void) {
                "Initialize /etc/machine-id from a random source.\n\n"
                "  -h --help             Show this help\n"
                "     --version          Show package version\n"
-               "     --root             Filesystem root\n",
+               "     --root=ROOT        Filesystem root\n",
                program_invocation_short_name);
 
         return 0;
@@ -87,7 +87,7 @@ static int parse_argv(int argc, char *argv[]) {
         }
 
         if (optind < argc) {
-                help();
+                log_error("Extraneous arguments");
                 return -EINVAL;
         }