Cannot convert type `System.Collections.Generic.KeyValuePair<string,string>' to `System.Collections.DictionaryEntry'

[middleJack]

Assets/Plugins/UnityHTTP-master/src/Request.cs(80,13): error CS0030: Cannot convert type System.Collections.Generic.KeyValuePair<string,string>' toSystem.Collections.DictionaryEntry'

Fixed it by replacing:
foreach ( DictionaryEntry entry in form.headers )

for:
foreach ( KeyValuePair<string, string> entry in form.headers )

BTW: Why is this library overwriting JSON class?