diff --git a/AUTHORS b/AUTHORS
index e12bd99..9aceb6b 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -2,6 +2,10 @@ Aidan Thornton:
     Added Maple Mini support.
 	board/board-maple-mini.h
 
+Jeremy Drake:
+    Modified STM32F103 support.
+	mcu/sys-stm32f103.c
+
 Kaz Kojima:
     Added STM32 Primer2 support.
 	board/board-stm32-primer2.h
diff --git a/ChangeLog b/ChangeLog
index c5c56c4..065a9d1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-08-03  Jeremy Drake <jeremydrake+gnuk@eacceleration.com>
+
+	* mcu/sys-stm32f103.c (flash_write): Allow compile time
+	flash size definition by STM32F103_OVERRIDE_FLASH_SIZE_KB.
+
 2017-08-02  NIIBE Yutaka  <gniibe@fsij.org>
 
 	* contrib/adc-gnu-linux.c: New.
diff --git a/mcu/sys-stm32f103.c b/mcu/sys-stm32f103.c
index 05e1f2f..81d8ec1 100644
--- a/mcu/sys-stm32f103.c
+++ b/mcu/sys-stm32f103.c
@@ -213,7 +213,11 @@ static int
 flash_write (uint32_t dst_addr, const uint8_t *src, size_t len)
 {
   int status;
+#if defined(STM32F103_OVERRIDE_FLASH_SIZE_KB)
+  uint32_t flash_end = FLASH_START_ADDR + STM32F103_OVERRIDE_FLASH_SIZE_KB*1024;
+#else
   uint32_t flash_end = FLASH_START_ADDR + (*FLASH_SIZE_REG)*1024;
+#endif
 
   if (dst_addr < FLASH_START || dst_addr + len > flash_end)
     return 0;
@@ -269,7 +273,11 @@ static void __attribute__((naked))
 flash_erase_all_and_exec (void (*entry)(void))
 {
   uint32_t addr = FLASH_START;
+#if defined(STM32F103_OVERRIDE_FLASH_SIZE_KB)
+  uint32_t end = FLASH_START_ADDR + STM32F103_OVERRIDE_FLASH_SIZE_KB*1024;
+#else
   uint32_t end = FLASH_START_ADDR + (*FLASH_SIZE_REG)*1024;
+#endif
   uint32_t page_size = 1024;
   int r;