diff --git a/sbin/ngcp-sync-grants b/sbin/ngcp-sync-grants
index 1ba12c1a..5ddbbcdc 100755
--- a/sbin/ngcp-sync-grants
+++ b/sbin/ngcp-sync-grants
@@ -348,7 +348,7 @@ sub grants_helper {
     my $host = $TEMP_GRANT_HOST;
 
     set_user_protected_password($user, $host);
-    $dbh->do("REVOKE ALL PRIVILEGES, GRANT OPTION FROM $user\@$host");
+    $dbh->do("REVOKE ALL PRIVILEGES, GRANT OPTION FROM '$user'\@'$host'");
 
     foreach my $grant (@$grants) {
         $grant = normalise_grant_str($grant);
@@ -365,7 +365,7 @@ sub grants_helper {
     }
 
     my $temp_grants = $dbh->selectall_arrayref(
-        "SHOW GRANTS FOR ?\@?", undef, $user, $host);
+        "SHOW GRANTS FOR '$user'\@'$host'");
 
     for (my $i=0;$i<=$#$temp_grants;$i++) {
         if ($temp_grants->[$i][0] =~ /grant usage/i) {
@@ -421,7 +421,7 @@ sub check_grants {
     my ($grants, $user, $host) = @_;
 
     my $current_grants = $dbh->selectall_arrayref(
-        "SHOW GRANTS FOR ?\@?", undef, $user, $host);
+        "SHOW GRANTS FOR '$user'\@'$host'");
     if ($DBI::errstr
         && ($DBI::errstr !~ /There is no such grant defined/ &&
             $DBI::errstr !~ /fetch[()]+ without execute[()]+/)) {