diff --git a/platformio.ini b/platformio.ini
index 45c62843..348c34e8 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -282,6 +282,7 @@ AR_lib_deps =  ;; for pre-usermod-library platformio_override compatibility
 
 [esp32_idf_V4]
 ;; build environment for ESP32 using ESP-IDF 4.4.x / arduino-esp32 v2.0.5
+;; *** important: build flags from esp32_idf_V4 are inherited by _all_ esp32-based MCUs: esp32, esp32s2, esp32s3, esp32c3
 ;;
 ;; please note that you can NOT update existing ESP32 installs with a "V4" build. Also updating by OTA will not work properly.
 ;; You need to completely erase your device (esptool erase_flash) first, then install the "V4" build from VSCode+platformio.
@@ -294,7 +295,6 @@ build_flags = -g
   -Wshadow=compatible-local ;; emit warning in case a local variable "shadows" another local one
   -DARDUINO_ARCH_ESP32 -DESP32
   ${esp32_all_variants.build_flags}
-  -DARDUINO_USB_CDC_ON_BOOT=0 ;; this flag is mandatory for "classic ESP32" when building with arduino-esp32 >=2.0.3
   -D WLED_ENABLE_DMX_INPUT
 lib_deps =
   ${esp32_all_variants.lib_deps}
@@ -475,6 +475,7 @@ platform_packages = ${esp32_idf_V4.platform_packages}
 custom_usermods = audioreactive
 build_unflags = ${common.build_unflags}
 build_flags = ${common.build_flags} ${esp32_idf_V4.build_flags} -D WLED_RELEASE_NAME=\"ESP32_8M\" #-D WLED_DISABLE_BROWNOUT_DET
+  -DARDUINO_USB_CDC_ON_BOOT=0 ;; this flag is mandatory for "classic ESP32" when building with arduino-esp32 >=2.0.3
 lib_deps = ${esp32_idf_V4.lib_deps}
 monitor_filters = esp32_exception_decoder
 board_build.partitions = ${esp32.large_partitions}
@@ -490,6 +491,7 @@ platform_packages = ${esp32_idf_V4.platform_packages}
 custom_usermods = audioreactive
 build_unflags = ${common.build_unflags}
 build_flags = ${common.build_flags} ${esp32_idf_V4.build_flags} -D WLED_RELEASE_NAME=\"ESP32_16M\" #-D WLED_DISABLE_BROWNOUT_DET
+              -DARDUINO_USB_CDC_ON_BOOT=0 ;; this flag is mandatory for "classic ESP32" when building with arduino-esp32 >=2.0.3
 lib_deps = ${esp32_idf_V4.lib_deps}
 monitor_filters = esp32_exception_decoder
 board_build.partitions = ${esp32.extreme_partitions}
@@ -506,6 +508,7 @@ upload_speed = 921600
 custom_usermods = audioreactive
 build_unflags = ${common.build_unflags}
 build_flags = ${common.build_flags} ${esp32.build_flags} -D WLED_RELEASE_NAME=\"ESP32_Ethernet\" -D RLYPIN=-1 -D WLED_USE_ETHERNET -D BTNPIN=-1
+  -DARDUINO_USB_CDC_ON_BOOT=0 ;; this flag is mandatory for "classic ESP32" when building with arduino-esp32 >=2.0.3
 ;  -D WLED_DISABLE_ESPNOW ;; ESP-NOW requires wifi, may crash with ethernet only
 lib_deps = ${esp32.lib_deps}
 board_build.partitions = ${esp32.default_partitions}
@@ -520,6 +523,7 @@ board_build.partitions = ${esp32.extended_partitions}
 custom_usermods = audioreactive
 build_unflags = ${common.build_unflags}
 build_flags = ${common.build_flags} ${esp32_idf_V4.build_flags} -D WLED_RELEASE_NAME=\"ESP32_WROVER\"
+  -DARDUINO_USB_CDC_ON_BOOT=0 ;; this flag is mandatory for "classic ESP32" when building with arduino-esp32 >=2.0.3
   -DBOARD_HAS_PSRAM -mfix-esp32-psram-cache-issue ;; Older ESP32 (rev.<3) need a PSRAM fix (increases static RAM used) https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-guides/external-ram.html
   -D DATA_PINS=25
 lib_deps = ${esp32_idf_V4.lib_deps}