diff --git a/variants/nicerf_lr2021/platformio.ini b/variants/nicerf_lr2021/platformio.ini
index 0f02a9ab..58ed7cd6 100644
--- a/variants/nicerf_lr2021/platformio.ini
+++ b/variants/nicerf_lr2021/platformio.ini
@@ -22,6 +22,8 @@ build_flags =
   -D WRAPPER_CLASS=CustomLR2021Wrapper
   -D LORA_TX_POWER=22
   -D RADIOLIB_EXCLUDE_SX126X=1
+  ; LR2021 IRQ DIO pin (configurable — LR2021 supports any DIO pin for IRQ)
+  -D LR2021_IRQ_DIO=9
 build_src_filter = ${esp32_base.build_src_filter}
   +<../variants/nicerf_lr2021>
   +<helpers/sensors>