GCC 7 warning: this statement may fall through [-Wimplicit-fallthrough=]

In file included from prog.cc:9:0:
ArduinoJson.h: In function 'T ArduinoJson::Polyfills::parseInteger(const char*) [with T = long int]':
ArduinoJson.h:3164:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
       negative_result = true;
       ^~~~~~~~~~~~~~~
ArduinoJson.h:3165:5: note: here
     case '+':
     ^~~~
ArduinoJson.h: In function 'T ArduinoJson::Polyfills::parseFloat(const char*) [with T = double]':
ArduinoJson.h:3099:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
       negative_result = true;
       ^~~~~~~~~~~~~~~
ArduinoJson.h:3100:5: note: here
     case '+':
     ^~~~