highlighting doesn't work for nested queries, even with _source enabled

nested_query_highlighting

curl -XDELETE 'localhost:9200/test'

curl -XPOST 'localhost:9200/test' -d '                                                                                                                        
{                                                                                                                                                             
    "settings": {                                                                                                                                             
        "number_of_replicas": 0,                                                                                                                              
        "number_of_shards": 1                                                                                                                                 
    },                                                                                                                                                        
    "mappings": {                                                                                                                                             
        "author": {                                                                                                                                           
            "properties": {                                                                                                                                   
                "name": { "type": "string" },                                                                                                                 
                "gender": { "type": "string" },                                                                                                               
                "book": {                                                                                                                                     
                    "type" : "nested",                                                                                                                        
                    "properties": {                                                                                                                           
                        "title": { "type": "string" }                                                                                                         
                    }                                                                                                                                         
                }                                                                                                                                             
            }                                                                                                                                                 
        }                                                                                                                                                     
    }                                                                                                                                                         
}'

curl -XPOST 'localhost:9200/test/author/1?refresh' -d '                                                                                                       
{                                                                                                                                                             
    "name": "simone de beauvoir",                                                                                                                             
    "gender": "female",                                                                                                                                       
    "book": {                                                                                                                                                 
        "title": "the ethics of ambiguity"                                                                                                                    
    }                                                                                                                                                         
}'

# fails to produce highlights
curl -XPOST 'localhost:9200/test/author/_search?pretty' -d '                                                                                                  
{                                                                                                                                                             
    "query": {                                                                                                                                                
        "nested": {                                                                                                                                           
            "query": {                                                                                                                                        
                "match": { "book.title": "ethics" }                                                                                                               
             },                                                                                                                                               
             "path": "book"                                                                                                                                   
        }                                                                                                                                                     
    },                                                                                                                                                        
    "highlight": {                                                                                                                                            
        "fields": {                                                                                                                                           
            "book.title" : {}                                                                                                                                 
        }                                                                                                                                                     
    }                                                                                                                                                         
}'

# also fails
curl -XPOST 'localhost:9200/test/author/_search?pretty' -d '                                                                                                  
{                                                                                                                                                             
    "query": {                                                                                                                                                
        "match": { "name": "simone" }                                                                                                                         
    },                                                                                                                                                        
    "highlight": {                                                                                                                                            
        "fields": {                                                                                                                                           
            "book.title" : {                                                                                                                                  
                "highlight_query": {                                                                                                                          
                    "nested": {                                                                                                                               
                        "query": {                                                                                                                            
                            "match": { "book.title": "ethics" }                                                                                              
                        },                                                                                                                                    
                        "path": "book"                                                                                                                        
                    }                                                                                                                                         
                }                                                                                                                                             
            }                                                                                                                                                 
        }                                                                                                                                                     
    }                                                                                                                                                         
}'

# succeeds
curl -XPOST 'localhost:9200/test/author/_search?pretty' -d '                                                                                                  
{                                                                                                                                                             
    "query": {                                                                                                                                                
        "match": { "name": "simone" }                                                                                                                         
    },                                                                                                                                                        
    "highlight": {                                                                                                                                            
        "fields": {                                                                                                                                           
            "book.title" : {                                                                                                                                  
                "highlight_query": {                                                                                                                          
                    "match": { "book.title": "ethics" }                                                                                                      
                }                                                                                                                                             
            }                                                                                                                                                 
        }                                                                                                                                                     
    }                                                                                                                                                         
}'