diff --git a/cpu/esp8266/Makefile.include b/cpu/esp8266/Makefile.include
index 98122c0240..6415d899a4 100644
--- a/cpu/esp8266/Makefile.include
+++ b/cpu/esp8266/Makefile.include
@@ -141,7 +141,7 @@ LINKFLAGS += -nostdlib -lgcc -u ets_run -Wl,-gc-sections # -Wl,--print-gc-sectio
 FLASHFILE ?= $(ELFFILE)
 
 # configure preflasher to convert .elf to .bin before flashing
-FLASH_SIZE = -fs 1MB
+FLASH_SIZE = -fs 8m
 PREFLASHER ?= esptool.py
 PREFFLAGS  ?= elf2image $(FLASH_SIZE) $(FLASHFILE)
 FLASHDEPS  += preflash