diff --git a/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_defines.h b/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_defines.h
index 63701ca334..4a252772cb 100644
--- a/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_defines.h
+++ b/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_defines.h
@@ -25,8 +25,6 @@
  * Native/Simulator LCD-specific defines
  */
 
-void usleep(uint64_t microsec);
-
 uint8_t u8g_com_sw_spi_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_val, void *arg_ptr);
 uint8_t u8g_com_ST7920_sw_spi_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_val, void *arg_ptr);
 
diff --git a/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_pin_routines.cpp b/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_pin_routines.cpp
index 91b7e0f67f..3566528079 100644
--- a/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_pin_routines.cpp
+++ b/Marlin/src/HAL/NATIVE_SIM/u8g/LCD_pin_routines.cpp
@@ -43,7 +43,6 @@ void u8g_SetPinOutput(uint8_t internal_pin_number) { SET_DIR_OUTPUT(internal_pin
 void u8g_SetPinInput(uint8_t internal_pin_number) { SET_DIR_INPUT(internal_pin_number); }
 void u8g_SetPinLevel(uint8_t pin, uint8_t pin_status) { WRITE_PIN(pin, pin_status); }
 uint8_t u8g_GetPinLevel(uint8_t pin) { return READ_PIN(pin); }
-void usleep(uint64_t microsec) { assert(false); /* why we here? */ }
 
 #ifdef __cplusplus
   }