diff --git a/PVE/API2Tools.pm b/PVE/API2Tools.pm
index a3d7ca84..618c13b3 100644
--- a/PVE/API2Tools.pm
+++ b/PVE/API2Tools.pm
@@ -17,14 +17,22 @@ use PVE::SafeSyslog;
 use PVE::Storage::Plugin;
 
 my $hwaddress;
+my $hwaddress_st = {};
 
 sub get_hwaddress {
-
-    return $hwaddress if defined ($hwaddress);
-
     my $fn = '/etc/ssh/ssh_host_rsa_key.pub';
+    my $st = stat($fn);
+
+    if (defined($hwaddress)
+	&& $hwaddress_st->{mtime} == $st->mtime
+	&& $hwaddress_st->{ino} == $st->ino
+	&& $hwaddress_st->{dev} == $st->dev) {
+	return $hwaddress;
+    }
+
     my $sshkey = PVE::Tools::file_get_contents($fn);
     $hwaddress = uc(md5_hex($sshkey));
+    $hwaddress_st->@{'mtime', 'ino', 'dev'} = ($st->mtime, $st->ino, $st->dev);
 
     return $hwaddress;
 }