diff --git a/ion/src/device/bootloader/drivers/external_flash.cpp b/ion/src/device/bootloader/drivers/external_flash.cpp
index 34de8b591..1c7686cd4 100644
--- a/ion/src/device/bootloader/drivers/external_flash.cpp
+++ b/ion/src/device/bootloader/drivers/external_flash.cpp
@@ -471,6 +471,7 @@ void __attribute__((noinline)) WriteMemory(uint8_t * destination, const uint8_t
   if (Config::NumberOfSectors == 0) {
     return;
   }
+  destination -= ExternalFlash::Config::StartAddress;
   unset_memory_mapped_mode();
   /* Each 256-byte page of the external flash memory (contained in a previously erased area)
    * may be programmed in burst mode with a single Page Program instruction.
diff --git a/ion/src/device/bootloader/drivers/external_flash_tramp.cpp b/ion/src/device/bootloader/drivers/external_flash_tramp.cpp
index 031722356..29a2bf03e 100644
--- a/ion/src/device/bootloader/drivers/external_flash_tramp.cpp
+++ b/ion/src/device/bootloader/drivers/external_flash_tramp.cpp
@@ -371,7 +371,7 @@ void MassErase() {
 
 void WriteMemory(uint8_t * destination, const uint8_t * source, size_t length) {
   asm("cpsid if");
-  reinterpret_cast<void(*)(uint8_t*, const uint8_t*, size_t)>(Ion::Device::Trampoline::address(Ion::Device::Trampoline::ExternalFlashWriteMemory))(destination + ExternalFlash::Config::StartAddress, source, length);
+  reinterpret_cast<void(*)(uint8_t*, const uint8_t*, size_t)>(Ion::Device::Trampoline::address(Ion::Device::Trampoline::ExternalFlashWriteMemory))(destination, source, length);
   asm("cpsie if");
 }
 
diff --git a/ion/src/device/n0110/drivers/external_flash.cpp b/ion/src/device/n0110/drivers/external_flash.cpp
index 1c9c4a1e9..612efc017 100644
--- a/ion/src/device/n0110/drivers/external_flash.cpp
+++ b/ion/src/device/n0110/drivers/external_flash.cpp
@@ -471,6 +471,7 @@ void __attribute__((noinline)) WriteMemory(uint8_t * destination, const uint8_t
   if (Config::NumberOfSectors == 0) {
     return;
   }
+  destination -= ExternalFlash::Config::StartAddress;
   unset_memory_mapped_mode();
   /* Each 256-byte page of the external flash memory (contained in a previously erased area)
    * may be programmed in burst mode with a single Page Program instruction.
diff --git a/ion/src/device/shared/drivers/flash.cpp b/ion/src/device/shared/drivers/flash.cpp
index 6f569cd89..692bd4df8 100644
--- a/ion/src/device/shared/drivers/flash.cpp
+++ b/ion/src/device/shared/drivers/flash.cpp
@@ -46,7 +46,7 @@ void WriteMemory(uint8_t * destination, uint8_t * source, size_t length) {
   if (SectorAtAddress((uint32_t)destination) < InternalFlash::Config::NumberOfSectors) {
     InternalFlash::WriteMemory(destination, source, length);
   } else {
-    ExternalFlash::WriteMemory(destination - ExternalFlash::Config::StartAddress, source, length);
+    ExternalFlash::WriteMemory(destination, source, length);
   }
 }