diff --git a/cpu/esp8266/Makefile.include b/cpu/esp8266/Makefile.include
index 8154de5cf221b..507949536ed0c 100644
--- a/cpu/esp8266/Makefile.include
+++ b/cpu/esp8266/Makefile.include
@@ -132,7 +132,7 @@ LINKFLAGS += -Wl,--warn-unresolved-symbols
 FLASHFILE ?= $(ELFFILE)
 
 # configure preflasher to convert .elf to .bin before flashing
-FLASH_SIZE = -fs 8m
+FLASH_SIZE = -fs 1MB
 PREFLASHER ?= esptool.py
 PREFFLAGS  ?= elf2image $(FLASH_SIZE) $(FLASHFILE)
 FLASHDEPS  += preflash