Value.IsValid() returns true on empty strings in structs

I have some code that uses reflection to check for missing values in some structs. Here's a simplified version of if:

package main

import (
    "fmt"
    "reflect"
)

type Foo struct {
    bar string
}

func main() {
    foo := Foo{}
    v := reflect.ValueOf(foo)
    fmt.Println("bar has a value:", v.FieldByName("bar").IsValid())
}

(Playground: http://ift.tt/2hYOJgp)

I expected this to print "false", but it actually prints "true".

The golang documentation for Value.IsValid() states that "It returns false if v is the zero Value". AFAIK, the zero value for a string is an empty string.

I made it work by adding an additional check:

if f.Kind() == reflect.String && f.String() == "" { 

But it feels kind of dirty and wrong. Any insight into why IsValid behaves the way it does?