diff --git a/boards/common/esp32/Makefile.include b/boards/common/esp32/Makefile.include
index 5087328682df..4a005b0d3a43 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 44a141a366b3..bde04dbd4194 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 b554ba56e746..645a83a9da63 100644
--- a/cpu/esp32/Makefile.include
+++ b/cpu/esp32/Makefile.include
@@ -159,7 +159,7 @@ 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 f60655f46245..507949536ed0 100644
--- a/cpu/esp8266/Makefile.include
+++ b/cpu/esp8266/Makefile.include
@@ -132,10 +132,10 @@ 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
+FLASHDEPS  += preflash
 
 # flasher configuration
 ifeq ($(QEMU), 1)