diff --git a/variants/stm32/CDEBYTE_E77-MBL/platformio.ini b/variants/stm32/CDEBYTE_E77-MBL/platformio.ini
index 290982405f..dfb36c014b 100644
--- a/variants/stm32/CDEBYTE_E77-MBL/platformio.ini
+++ b/variants/stm32/CDEBYTE_E77-MBL/platformio.ini
@@ -7,8 +7,11 @@ build_flags =
   ${stm32_base.build_flags}
   -Ivariants/stm32/CDEBYTE_E77-MBL
   -DSERIAL_UART_INSTANCE=1
-  -DPIN_SERIAL_RX=PA3
-  -DPIN_SERIAL_TX=PA2
+  -DPIN_SERIAL_RX=PB7
+  -DPIN_SERIAL_TX=PB6
+  -DENABLE_HWSERIAL2
+  -DPIN_SERIAL2_TX=PA2
+  -DPIN_SERIAL2_RX=PA3
   -DMESHTASTIC_EXCLUDE_ENVIRONMENTAL_SENSOR=1
   -DMESHTASTIC_EXCLUDE_I2C=1
   -DMESHTASTIC_EXCLUDE_GPS=1