diff --git a/installer/data/mysql/atomicupdate/bug18801.perl b/installer/data/mysql/atomicupdate/bug18801.perl
new file mode 100644
index 0000000000..8a8fd50615
--- /dev/null
+++ b/installer/data/mysql/atomicupdate/bug18801.perl
@@ -0,0 +1,15 @@
+$DBversion = 'XXX';  # will be replaced by the RM
+if( CheckVersion( $DBversion ) ) {
+    # Fetch all auth types
+    my $authtypes = $dbh->selectcol_arrayref( q|SELECT authtypecode FROM auth_types| );
+
+    if( grep { $_ eq 'Default' } @$authtypes ) {
+        # If this exists as an authtypecode, we don't do anything
+    } else {
+        # Replace the incorrect Default by empty string
+        $dbh->do( q|UPDATE auth_header SET authtypecode='' WHERE authtypecode='Default'| );
+    }
+
+    SetVersion( $DBversion );
+    print "Upgrade to $DBversion done (Bug 18801 - Update incorrect Default auth type codes)\n";
+}