diff --git a/platformio.ini b/platformio.ini
index 7448d5d..fbf14ad 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -556,7 +556,7 @@ build_flags =
   '-DESP32_ETHERNET=true'
   '-DETH_PHY_ADDR=1'
   '-DETH_PHY_POWER=16'
-  '-Ddefine ETH_CLK_MODE=ETH_CLOCK_GPIO0_IN'
+  '-DETH_CLK_MODE=ETH_CLOCK_GPIO0_IN'
   '-DGateway_Name="OpenMQTTGateway_ESP32_WT32-ETH01"'
 
 [env:esp32-olimex-gtw-ble-wifi]