No idea why this is necessary...

platformio.ini

@@ -24,7 +24,7 @@ lib_deps_external =
   CircularBuffer@~1.2.0
 extra_scripts =
   pre:.build_web.py
-build_flags = !python .get_version.py -DMQTT_MAX_PACKET_SIZE=200 -DHTTP_UPLOAD_BUFLEN=128 -D FIRMWARE_NAME=milight-hub -Idist
+build_flags = !python .get_version.py -DMQTT_MAX_PACKET_SIZE=200 -DHTTP_UPLOAD_BUFLEN=128 -D FIRMWARE_NAME=milight-hub -Idist -Ilib/DataStructures
 # -D STATE_DEBUG
 # -D DEBUG_PRINTF
 # -D MQTT_DEBUG