What is the JsonPath expression for selecting an object based on sub-object values?

Question

I need to be able to select elements within a JSON document based on the values in sub-elements which, unfortunately, reside in a list of key-value pairs (this is the structure I have to work with). I'm using Jayway 2.4.0.

Here is the JSON document:

{
    "topLevelArray": [
        {
            "elementId": "Elem1",
            "keyValuePairs": [
                {
                    "key": "Length",
                    "value": "10"
                },
                {
                    "key": "Width",
                    "value": "3"
                },
                {
                    "key": "Producer",
                    "value": "alpha"
                }
            ]
        },
        {
            "elementId": "Elem2",
            "keyValuePairs": [
                {
                    "key": "Length",
                    "value": "20"
                },
                {
                    "key": "Width",
                    "value": "8"
                },
                {
                    "key": "Producer",
                    "value": "beta"
                }
            ]
        },
        {
            "elementId": "Elem3",
            "keyValuePairs": [
                {
                    "key": "Length",
                    "value": "15"
                },
                {
                    "key": "Width",
                    "value": "5"
                },
                {
                    "key": "Producer",
                    "value": "beta"
                }
            ]
        }
    ]
}

Here is the JsonPath I thought would do the trick:

$..topLevelArray[ ?( @.keyValuePairs[ ?(@.key=='Producer' && @.value=='beta') ] ) ]

and

$.topLevelArray[ ?( @.keyValuePairs[ ?(@.key=='Producer' && @.value=='beta') ] ) ]

Unfortunately, both are returning everything in the list, including the entry with Producer of 'alpha'. Thx in advance.