diff --git a/src/warden-server/bin/unregisterClient.pl b/src/warden-server/bin/unregisterClient.pl
index 1fe3778cfa2bc5c67197e6d0316ecf2d1b98e530..db4d62b64a0f2346bd95a7f48f98b658ca52fcd5 100755
--- a/src/warden-server/bin/unregisterClient.pl
+++ b/src/warden-server/bin/unregisterClient.pl
@@ -95,17 +95,18 @@ if ($help) {
 
 # catch version option
 if ($script_version) {
-	  version;
+  version;
 }
 
 # check parameters definition
-if (!defined $client_id) {
-  WardenCommon::errMsg("Parameter 'client_id' is not defined!");
+if ($client_id !~ /^\d+\z/) {
+  WardenCommon::errMsg("Parameter '-i <client_id>' is not a integer");
 }
 
 # connect to DB
 my $dbh = WardenCommon::connectDB($WardenCommon::DB_NAME, $WardenCommon::DB_HOST, $WardenCommon::DB_USER, $WardenCommon::DB_PASS);
 
+# obtain a server hostname
 my $warden_server = WardenCommon::trim(`hostname -f`);
 
 # check if client has been already registered
@@ -114,7 +115,7 @@ $sth->execute($client_id) or die "Cannot execute statement: " . $sth->errstr;
 my ($id, $hostname, $service, $client_type, $type) = $sth->fetchrow();
 
 # delete registered client
-if (!defined $id) {
+unless (defined $id) {
   sendMsg("err", "Attempt to delete unregister client [Client_id: '$client_id'] from Warden server '$warden_server'");
   WardenCommon::errMsg("Client (#$client_id) is not registered at Warden server '$warden_server'");
 } else {