With the release of the Arduino ESP8266 2.4.2 core, there is a new build flag that should be added to platformio.ini (at least as a comment). The new default behavior is to disable WPS support in order to free 4K of additional memory. To restore WPS support (so code that worked previously will still work), the following build flag should be added:
-D NO_EXTRA_4K_HEAP
This behavior will be automatic in the 2.5.0 release.