diff --git a/boards/common/esp32/Makefile.include b/boards/common/esp32/Makefile.include
index 5087328682..4a005b0d3a 100644
--- a/boards/common/esp32/Makefile.include
+++ b/boards/common/esp32/Makefile.include
@@ -8,4 +8,5 @@ PORT_DARWIN ?= $(firstword $(sort $(wildcard /dev/tty.SLAB_USBtoUART*)))
 include $(RIOTMAKE)/tools/serial.inc.mk
 
 # reset tool configuration
-RESET ?= esptool.py --before default_reset run
+RESET ?= esptool.py
+RESET_FLAGS ?= --port $(PORT) --before default_reset run
diff --git a/boards/common/esp8266/Makefile.include b/boards/common/esp8266/Makefile.include
index 44a141a366..bde04dbd41 100644
--- a/boards/common/esp8266/Makefile.include
+++ b/boards/common/esp8266/Makefile.include
@@ -8,4 +8,5 @@ PORT_DARWIN ?= $(firstword $(sort $(wildcard /dev/tty.SLAB_USBtoUART*)))
 include $(RIOTMAKE)/tools/serial.inc.mk
 
 # reset tool configuration
-RESET ?= esptool.py --before default_reset run
+RESET ?= esptool.py
+RESET_FLAGS ?= --port $(PORT) --before default_reset run
diff --git a/cpu/esp32/Makefile.include b/cpu/esp32/Makefile.include
index f3816578ea..00db66f4a0 100644
--- a/cpu/esp32/Makefile.include
+++ b/cpu/esp32/Makefile.include
@@ -175,7 +175,7 @@ PREFFLAGS += ls -l $(FLASHFILE).bin | awk '{ print $$5 }' >> $(BINDIR)/partition
 
 PREFFLAGS += python $(RIOTCPU)/$(CPU)/gen_esp32part.py --disable-sha256sum
 PREFFLAGS += --verify $(BINDIR)/partitions.csv $(BINDIR)/partitions.bin
-FLASHDEPS  = preflash
+FLASHDEPS += preflash
 
 # flasher configuration
 ifeq ($(QEMU), 1)
diff --git a/cpu/esp8266/Makefile.include b/cpu/esp8266/Makefile.include
index 786e542fa3..98122c0240 100644
--- a/cpu/esp8266/Makefile.include
+++ b/cpu/esp8266/Makefile.include
@@ -141,10 +141,10 @@ 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 8m
+FLASH_SIZE = -fs 1MB
 PREFLASHER ?= esptool.py
 PREFFLAGS  ?= elf2image $(FLASH_SIZE) $(FLASHFILE)
-FLASHDEPS  ?= preflash
+FLASHDEPS  += preflash
 
 # flasher configuration
 ifeq ($(QEMU), 1)