diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm
index 5cbaa820..53855acc 100644
--- a/PVE/API2/Qemu.pm
+++ b/PVE/API2/Qemu.pm
@@ -293,7 +293,12 @@ __PACKAGE__->register_method({
     },
     returns => { 
 	type => "object",
-	properties => {},
+	properties => {
+	    digest => {
+		type => 'string',
+		description => 'SHA1 digest of configuration file. This can be used to prevent concurrent modifications.',
+	    }
+	},
     },
     code => sub {
 	my ($param) = @_;
@@ -332,6 +337,12 @@ __PACKAGE__->register_method({
 		    optional => 1,
 		    requires => 'delete',
 		},
+		digest => {
+		    type => 'string',
+		    description => 'Prevent changes if current configuration file has different SHA1 digest. This can be used to prevent concurrent modifications.',
+		    maxLength => 40,
+		    optional => 1,		    
+		}
 	    }),
     },
     returns => { type => 'null'},
@@ -356,6 +367,8 @@ __PACKAGE__->register_method({
 
 	die "no options specified\n" if !$delete && !scalar(keys %$param);
 
+	my $digest = extract_param($param, 'digest');
+
 	my $storecfg = PVE::Storage::config(); 
 
 	&$resolve_cdrom_alias($param);
@@ -396,6 +409,9 @@ __PACKAGE__->register_method({
 
 	    my $conf = PVE::QemuServer::load_config($vmid);
 
+	    die "checksum missmatch (file change by other user?)\n" 
+		if $digest && $digest ne $conf->{digest};
+
 	    PVE::QemuServer::check_lock($conf) if !$skiplock;
 
 	    foreach my $opt (keys %$eject) {
diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 8613ba3b..8e0352d6 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -1323,7 +1323,9 @@ sub parse_vm_config {
 
     return undef if !defined($raw);
 
-    my $res = {};
+    my $res = {
+	digest => Digest::SHA1::sha1_hex($raw),
+    };
 
     $filename =~ m|/qemu-server/(\d+)\.conf$| 
 	|| die "got strange filename '$filename'";
@@ -1408,6 +1410,7 @@ sub change_config_nolock {
     my $new_volids = {};
 
     foreach my $key (keys %$settings) {
+	next if $key eq 'digest';
 	my $value = $settings->{$key};
 	if ($key eq 'description') {
 	    $value = PVE::Tools::encode_text($value);
diff --git a/qm b/qm
index 546e08fa..7f572887 100755
--- a/qm
+++ b/qm
@@ -392,6 +392,7 @@ my $cmddef = {
 		{ node => $nodename }, sub {
 		    my $config = shift;
 		    foreach my $k (sort (keys %$config)) {
+			next if $k eq 'digest';
 			my $v = $config->{$k};
 			if ($k eq 'description') {
 			    $v = PVE::Tools::encode_text($v);