diff --git a/.github/arduino-ci/Dockerfile b/.github/arduino-ci/Dockerfile
index e7ce92a..be190ca 100644
--- a/.github/arduino-ci/Dockerfile
+++ b/.github/arduino-ci/Dockerfile
@@ -29,7 +29,9 @@ RUN arduino-cli core install arduino:mbed_opta
 RUN arduino-cli core install arduino:mbed_portenta
 RUN arduino-cli core install arduino:mbed_rp2040
 
-# install extra cores
+# Install extra cores.
+# NOTE: due to bug in arduino-cli the last core is installed by downloading
+# the index file, see: https://github.com/arduino/arduino-cli/issues/2345
 RUN arduino-cli config add board_manager.additional_urls \
     https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_dev_index.json && \
   arduino-cli config add board_manager.additional_urls \
diff --git a/.github/workflows/arduino-builds.yml b/.github/workflows/arduino-builds.yml
index 32976ab..d88cf12 100644
--- a/.github/workflows/arduino-builds.yml
+++ b/.github/workflows/arduino-builds.yml
@@ -47,7 +47,7 @@ jobs:
         example:
           - DallasTemperature
     env:
-      # -c added to make buggy esp32-arduino core happy,
+      # NOTE: `-c' option added to make buggy esp32-arduino core happy,
       # see: https://github.com/espressif/arduino-esp32/issues/8815
       BUILD_FLAGS: "-c \
         -DCONFIG_PWR_CTRL_ENABLED \