diff --git a/PVE/API2/Storage/Config.pm b/PVE/API2/Storage/Config.pm
index 3a6c6bc..7d3826e 100755
--- a/PVE/API2/Storage/Config.pm
+++ b/PVE/API2/Storage/Config.pm
@@ -254,6 +254,8 @@ __PACKAGE__->register_method ({
 	    },
 	    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,
 	    }
 	},
diff --git a/PVE/Storage.pm b/PVE/Storage.pm
index 7ee17c3..64b4c74 100755
--- a/PVE/Storage.pm
+++ b/PVE/Storage.pm
@@ -425,15 +425,13 @@ sub parse_config {
 
     my $ids = {};
 
-    my $sha1 = Digest::SHA1->new;
+    my $digest = Digest::SHA1::sha1_hex($raw);
 
     my $pri = 0;
 
     while ($raw && $raw =~ s/^(.*?)(\n|$)//) {
 	my $line = $1;
 
- 	$sha1->add ($line); # compute digest
-
 	next if $line =~ m/^\#/;
 	next if $line =~ m/^\s*$/;
 
@@ -526,8 +524,6 @@ sub parse_config {
 	}
     }
 
-    my $digest = $sha1->hexdigest;
-
     my $cfg = { ids => $ids, digest => $digest};
 
     return $cfg;