Intersect returns an empty list when the contents of the compared Collections are Maps

import org.junit.Test

class IntersectTest {
    @Test
    void testIntersect() {
        def list1 = [[language: 'Java'], [language: 'Groovy'], [language: 'Scala']]
        def list2 = [[language: 'Groovy'], [language: 'JRuby'], [language: 'Java']]
        def intersection = list1.intersect(list2)

        assert list1[0] == list2[2] // proves that there should be intersecting values
        println "Intersection: $intersection"
        assert intersection == [[language: 'Groovy'], [language: 'Java']]
    }
}

Intersection: []

Assertion failed: 

assert intersection == [[language: 'Groovy'], [language: 'Java']]
       |            |
       []           false