Assign String to key doesn't work

Created by: dcsoftware

Hi, I run into this issue and I don't know if I am doing something wrong or there is a problem in the library. When I assign a string value to a key in an object, what it is assigned is true value. I have a string received from Serial witch I cut into several substring and them create a json with this data. Here is a sample of my code:

char buff[64];

Serial.readBytesUntil(10, buff, sizeof(buff));

String s = buff;

StaticJsonBuffer<300> jsonBuffer;

JsonObject& root = jsonBuffer.createObject();

root["key"] = s.substring(10, 20); root["key1"] = s.substring(21, 28);

root.printTo(Serial);

The output is: {"key":true,"key1":true}

instead of having my substring it store a "true" value. Same thing happens if I do this:

String a = s.substring(10,20);

root["key"] = a;

Waiting for an answer a in the mean time, Thank very much for your awesome work!!!