Ambiguous overload for 'operator[]'

Created by: zgoda

I revisited my old code written against 5.6.x and found that in 5.8.1 I'm no longer allowed to use char[] variable as object key:

src/process.cpp: In member function 'bool ProcessManager::_loadConfig()':
src/process.cpp:38:33: error: ambiguous overload for 'operator[]' (operand types are 'ArduinoJson::JsonObject' and 'char [21]')
JsonArray& statesList = root[rootKeyBuf];

rootKeyBuf is regular C string variable so I can do sprintf() on it. It works if I cast it to const char *:

JsonArray& statesList = root[(const char *)rootKeyBuf];

Was that intentional?