diff --git a/Sming/Arch/Esp8266/Components/spi_flash/include/esp_spi_flash.h b/Sming/Arch/Esp8266/Components/spi_flash/include/esp_spi_flash.h
index cba56c919d..ebeb897a9b 100644
--- a/Sming/Arch/Esp8266/Components/spi_flash/include/esp_spi_flash.h
+++ b/Sming/Arch/Esp8266/Components/spi_flash/include/esp_spi_flash.h
@@ -68,8 +68,9 @@ typedef struct
  *  @note If memptr is not in valid flash memory it will return an offset which exceeds
  *  the internal flash memory size. This is caught by constructors using getMaxSize()
  *  to provide a zero-length extent.
+ *  @deprecated This function only works if rBoot is running from slot #0.
  */
-static inline uint32_t flashmem_get_address(const void* memptr)
+SMING_DEPRECATED static inline uint32_t flashmem_get_address(const void* memptr)
 {
 	return (uint32_t)memptr - INTERNAL_FLASH_START_ADDRESS;
 }