diff --git a/src/common/platforms/esp/stub_flasher.c b/src/common/platforms/esp/stub_flasher.c
index d733d359..09afcfe3 100644
--- a/src/common/platforms/esp/stub_flasher.c
+++ b/src/common/platforms/esp/stub_flasher.c
@@ -25,7 +25,7 @@
 #if defined(ESP8266)
 #include "eagle_soc.h"
 #include "ets_sys.h"
-#include "../../../miniz.c"
+#include "miniz.c"
 #elif defined(ESP32)
 #include "rom/efuse.h"
 #include "rom/miniz.h"
@@ -38,7 +38,7 @@
 #include "uart.h"
 
 /* Param: baud rate. */
-uint32_t params[1] __attribute__((section(".params")));
+uint32_t params[2] __attribute__((section(".params")));
 
 #define FLASH_BLOCK_SIZE 65536
 #define FLASH_SECTOR_SIZE 4096
@@ -477,8 +477,7 @@ uint8_t cmd_loop(void) {
 }
 
 void stub_main1(void) {
-  uint32_t baud_rate = params[0];
-  uint32_t greeting = 0x4941484f; /* OHAI */
+  uint32_t old_baud_rate = params[0], new_baud_rate = params[1];
   uint8_t last_cmd;
 
   /* This points at us right now, reset for next boot. */
@@ -487,6 +486,7 @@ void stub_main1(void) {
 /* Selects SPI functions for flash pins. */
 #if defined(ESP8266)
   SelectSpiFunction();
+  spi_flash_attach();
   SET_PERI_REG_MASK(0x3FF00014, 1); /* Switch to 160 MHz */
 #elif defined(ESP32)
   esp_rom_spiflash_attach(ets_efuse_get_spiconfig(), 0 /* legacy */);
@@ -496,9 +496,10 @@ void stub_main1(void) {
       0 /* deviceId */, 16 * 1024 * 1024 /* chip_size */, FLASH_BLOCK_SIZE,
       FLASH_SECTOR_SIZE, FLASH_PAGE_SIZE, 0xffff /* status_mask */);
 
-  if (baud_rate > 0) {
+  uint32_t old_div = 0;
+  if (new_baud_rate > 0) {
     ets_delay_us(10000);
-    set_baud_rate(0, baud_rate);
+    old_div = set_baud_rate(0, old_baud_rate, new_baud_rate);
   }
 
   /* Give host time to get ready too. */
@@ -509,7 +510,7 @@ void stub_main1(void) {
     WRITE_PERI_REG(UART_FIFO_REG(0), 0x55);
   }
 #else
-  SLIP_send(&greeting, 4);
+  SLIP_send(&old_div, 4);
 #endif
 
   last_cmd = cmd_loop();
@@ -525,7 +526,7 @@ void stub_main1(void) {
      * then jumps to 0x4000108a, then checks strapping bits again (which will
      * not have changed), and then proceeds to 0x400010a8.
      */
-    volatile uint32_t *sp = &baud_rate;
+    volatile uint32_t *sp = &old_baud_rate;
     while (*sp != (uint32_t) 0x40001100) sp++;
     *sp = 0x400010a8;
     /*
diff --git a/src/common/platforms/esp32/stubs/stub.ld b/src/common/platforms/esp32/stubs/stub.ld
index 6c2af65a..84085bb3 100644
--- a/src/common/platforms/esp32/stubs/stub.ld
+++ b/src/common/platforms/esp32/stubs/stub.ld
@@ -42,5 +42,10 @@ SECTIONS {
 INCLUDE "components/esp32/ld/esp32.rom.ld"
 INCLUDE "components/esp32/ld/esp32.rom.spiram_incompatible_fns.ld"
 
+PROVIDE(ets_isr_mask = 0x400067fc);
+PROVIDE(ets_isr_unmask = 0x40006808);
+PROVIDE(MD5Init = 0x4005da7c);
+PROVIDE(MD5Update = 0x4005da9c);
+PROVIDE(MD5Final = 0x4005db1c);
 PROVIDE(esp_rom_spiflash_attach = 0x40062a6c);
 PROVIDE(esp_rom_spiflash_config_clk = 0x40062bc8);
diff --git a/src/common/platforms/esp32/stubs/uart.c b/src/common/platforms/esp32/stubs/uart.c
index 8d2bca74..d6d1faad 100644
--- a/src/common/platforms/esp32/stubs/uart.c
+++ b/src/common/platforms/esp32/stubs/uart.c
@@ -19,9 +19,13 @@
 
 #include "rom_functions.h"
 
-void set_baud_rate(uint32_t uart_no, uint32_t baud_rate) {
-  uint32_t master_freq = ets_get_detected_xtal_freq() << 4;
-  master_freq += (baud_rate / 2);
-  uint32_t div = master_freq / baud_rate;
-  uart_div_modify(uart_no, div);
+uint32_t set_baud_rate(uint32_t uart_no, uint32_t old_baud_rate,
+                       uint32_t new_baud_rate) {
+  uint32_t uart_reg = REG_READ(UART_CLKDIV_REG(uart_no));
+  uint32_t uart_div = uart_reg & UART_CLKDIV_M;
+  uint32_t fraction = (uart_reg >> UART_CLKDIV_FRAG_S) & UART_CLKDIV_FRAG_V;
+  uart_div = (uart_div << 4) + fraction;
+  uint32_t master_freq = uart_div * old_baud_rate;
+  uart_div_modify(uart_no, master_freq / new_baud_rate);
+  return uart_div;
 }
diff --git a/src/common/platforms/esp32/stubs/uart.h b/src/common/platforms/esp32/stubs/uart.h
index b28edf88..99e351ac 100644
--- a/src/common/platforms/esp32/stubs/uart.h
+++ b/src/common/platforms/esp32/stubs/uart.h
@@ -20,6 +20,7 @@
 
 #include <stdint.h>
 
-void set_baud_rate(uint32_t uart_no, uint32_t baud_rate);
+uint32_t set_baud_rate(uint32_t uart_no, uint32_t old_baud_rate,
+                       uint32_t new_baud_rate);
 
 #endif /* CS_COMMON_PLATFORMS_ESP32_STUBS_UART_H_ */
diff --git a/src/common/platforms/esp8266/stubs/Makefile b/src/common/platforms/esp8266/stubs/Makefile
index 7aee5613..f7a76122 100644
--- a/src/common/platforms/esp8266/stubs/Makefile
+++ b/src/common/platforms/esp8266/stubs/Makefile
@@ -23,13 +23,13 @@ all: $(STUB_ELF)
 $(STUB_ELF): $(STUB) $(LIBS)
 	@echo "  CC   $^ -> $@"
 	@[ -d $(BUILD_DIR) ] || mkdir $(BUILD_DIR)
-	@docker run --rm -i -v $(CURDIR)/../../../..:/src $(SDK) //bin/bash -c \
+	docker run --rm -i -v $(CURDIR)/../../../..:/src $(SDK) //bin/bash -c \
     "cd /src/common/platforms/esp8266/stubs && \
      $(XT_CC) -std=c99 -Wall -Werror -Os -DESP8266 \
          -mtext-section-literals -mlongcalls -nostdlib -fno-builtin \
-         -I. -I/src/common/platforms/esp \
+         -I. -I/src/common/platforms/esp -I/src/common/platforms/esp8266 \
          -I/opt/Espressif/ESP8266_SDK \
-         -Wl,-static -ffunction-sections -Wl,--gc-sections \
+         -Wl,-static -ffunction-sections -lgcc -Wl,--gc-sections \
          -Tstub.ld $(CFLAGS) -o $@ $^"
 
 wrap: $(STUB_JSON)
diff --git a/src/common/platforms/esp8266/stubs/stub.ld b/src/common/platforms/esp8266/stubs/stub.ld
index f54a4f84..08c416c4 100644
--- a/src/common/platforms/esp8266/stubs/stub.ld
+++ b/src/common/platforms/esp8266/stubs/stub.ld
@@ -41,3 +41,4 @@ INCLUDE "eagle.rom.addr.v6.ld"
 PROVIDE(SPIFlashModeConfig = 0x40004568);
 PROVIDE(SPI_erase_sector = 0x400040c0);
 PROVIDE(SPI_erase_block = 0x40004120);
+PROVIDE(uart_div_modify = 0x400039d8);
diff --git a/src/common/platforms/esp8266/stubs/uart.c b/src/common/platforms/esp8266/stubs/uart.c
index cb99b2d9..39e28117 100644
--- a/src/common/platforms/esp8266/stubs/uart.c
+++ b/src/common/platforms/esp8266/stubs/uart.c
@@ -18,9 +18,15 @@
 #include "uart.h"
 #include "ets_sys.h"
 
-#define UART_CLKDIV_26MHZ(B) (52000000 + B / 2) / B
+#define UART_CLKDIV_M (UART_CLKDIV_CNT << UART_CLKDIV_S)
 
-void set_baud_rate(uint32_t uart_no, uint32_t baud_rate) {
-  uint32_t div = UART_CLKDIV_26MHZ(baud_rate);
-  WRITE_PERI_REG(UART_CLKDIV_REG(uart_no), div & 0xfffff);
+void uart_div_modify(uint8_t uart_no, uint32_t div);
+
+uint32_t set_baud_rate(uint32_t uart_no, uint32_t old_baud_rate,
+                       uint32_t new_baud_rate) {
+  uint32_t uart_reg = READ_PERI_REG(UART_CLKDIV_REG(uart_no));
+  uint32_t uart_div = uart_reg & UART_CLKDIV_M;
+  uint32_t master_freq = uart_div * old_baud_rate;
+  uart_div_modify(uart_no, master_freq / new_baud_rate);
+  return uart_div;
 }
diff --git a/src/common/platforms/esp8266/stubs/uart.h b/src/common/platforms/esp8266/stubs/uart.h
index ad3ef1dc..5afd9e38 100644
--- a/src/common/platforms/esp8266/stubs/uart.h
+++ b/src/common/platforms/esp8266/stubs/uart.h
@@ -20,9 +20,11 @@
 
 #include <stdint.h>
 
-void set_baud_rate(uint32_t uart_no, uint32_t baud_rate);
+#include "uart_register.h"
+
+uint32_t set_baud_rate(uint32_t uart_no, uint32_t old_baud_rate,
+                       uint32_t new_baud_rate);
 
-#define REG_UART_BASE(i) (0x60000000 + (i) *0xf00)
 #define UART_FIFO_REG(i) (REG_UART_BASE(i) + 0x0)
 #define UART_CONF1_REG(i) (REG_UART_BASE(i) + 0x24)
 #define UART_RX_TOUT_EN (BIT(31))