Weird get_query_var bug

// THIS WORKS IN WAMP

/**
 * Hook the WP parse_query action, check if we're supposed to be
 * processing an upload or not.
 *
 * @param object $query A WP_Query object
 * @return void
 **/
public function parse_query( $query ) {
    // Check the request relates to us
    if ( ! (bool) $query->get( 'mb_dlr_receipt' ) )
        return;
    $this->process_delivery_receipt();
    exit;
}

// THIS DOES NOT WORK IN WAMP, BUT DOES WORK FOR *NIX I BELIEVE


/**
 * Hook the WP parse_query action, check if we're supposed to be
 * processing an upload or not.
 *
 * @param object $query A WP_Query object
 * @return void
 **/
public function parse_query( $query ) {
    // Check the request relates to us
    if ( ! (bool) get_query_var( 'mlb_dlr_receipt' ) )
        return;
    $this->process_delivery_receipt();
    exit;
}

// AND HERE'S THE STACK TRACE



( ! ) Fatal error: Call to a member function get() on a non-object in C:\wamp\www\wp-includes\query.php on line 27
Call Stack
#   Time    Memory  Function    Location
1   0.0017  952928  {main}( )   ..\plugins.php:0
2   0.0023  1072480 require_once( 'C:\wamp\www\wp-admin\admin.php' )    ..\plugins.php:10
3   0.0025  1093304 require_once( 'C:\wamp\www\wp-load.php' )   ..\admin.php:30
4   0.0026  1111392 require_once( 'C:\wamp\www\wp-config.php' ) ..\wp-load.php:29
5   0.0031  1238456 require_once( 'C:\wamp\www\wp-settings.php' )   ..\wp-config.php:91
6   0.1583  28539480    include_once( 'C:\wamp\www\wp-content\plugins\jigoshop\jigoshop.php' )  ..\wp-settings.php:192
7   0.2047  35591416    jigoshop_singleton::instance( ) ..\jigoshop.php:104
8   0.2047  35591952    jigoshop_cart->__construct( )   ..\jigoshop_singleton.php:35
9   0.2047  35591952    jigoshop_cart->get_cart_from_session( ) ..\jigoshop_cart.class.php:43
10  0.2047  35593848    jigoshop_product->jigoshop_product( )   ..\jigoshop_cart.class.php:63
11  0.2057  35617632    jigoshop_product->get_children( )   ..\jigoshop_product.class.php:93
12  0.2057  35618048    get_children( ) ..\jigoshop_product.class.php:129
13  0.2058  35620272    get_posts( )    ..\post.php:298
14  0.2058  35629704    WP_Query->query( )  ..\post.php:1390
15  0.2058  35632504    WP_Query->get_posts( )  ..\query.php:2904
16  0.2058  35632640    WP_Query->parse_query( )    ..\query.php:1909
17  0.2061  35644128    do_action_ref_array( )  ..\query.php:1663
18  0.2061  35645168    call_user_func_array ( )    ..\plugin.php:486
19  0.2062  35645200    MBESMS->parse_query( )  ..\plugin.php:486
20  0.2062  35645280    get_query_var( )    ..\class-mbesms.php:128