Error in the shortcodes (attributes).

Ceased to be handled gracefully shortcodes in WP. For example, if you use [bartag foo = “foo-value”], then the function is activated, but the parameter “foo” is not transmitted. Because of this, there are errors in the function.
I tried to disable all plug-ins, but to no avail.

On the example it looks like this.

The code in functions.php:

function bartag_func( $atts ) {
	extract( shortcode_atts( array(
		'foo' => 'something',
		'bar' => 'something else',
	), $atts ) );
	return "foo = {$foo}";
}
add_shortcode( 'bartag', 'bartag_func' );

Shortcode to the editor:
[bartag foo="foo-value"]

Results per page:
foo = something

Although, according to the normal, the result should be a:
foo = foo-value

Please help deal with the problem.