t = db.jstests_in6;
t.drop();

t.save( {} );

function doTest() {
    assert.eq.automsg( "1", "t.count( {i:null} )" );
    assert.eq.automsg( "1", "t.count( {i:{$in:[null]}} )" );
}

doTest();
t.ensureIndex( {i:1} );
doTest();