diff --git a/ports/mimxrt10xx/boards/sparkfun_teensy_micromod/flash_config.c b/ports/mimxrt10xx/boards/sparkfun_teensy_micromod/flash_config.c
index 09886dece6..e0f5a5bd7d 100644
--- a/ports/mimxrt10xx/boards/sparkfun_teensy_micromod/flash_config.c
+++ b/ports/mimxrt10xx/boards/sparkfun_teensy_micromod/flash_config.c
@@ -15,7 +15,7 @@ __attribute__((section(".boot_hdr.ivt")))
  *  IVT Data
  *************************************/
 const ivt image_vector_table = {
-    IVT_HEADER,                       /* IVT Header */
+    0x432000D1,                       /* Teensy bootloader looks for this value*/
     IMAGE_ENTRY_ADDRESS,              /* Image Entry Function */
     IVT_RSVD,                         /* Reserved = 0 */
     (uint32_t)DCD_ADDRESS,            /* Address where DCD information is stored */
@@ -25,13 +25,15 @@ const ivt image_vector_table = {
     IVT_RSVD                          /* Reserved = 0 */
 };
 
+extern unsigned long _flashimagelen;
+
 __attribute__((section(".boot_hdr.boot_data")))
 /*************************************
  *  Boot Data
  *************************************/
 const BOOT_DATA_T boot_data = {
     FLASH_BASE,               /* boot start location */
-    FLASH_SIZE,               /* size */
+    (uint32_t)&_flashimagelen, /* actual size of image */
     PLUGIN_FLAG,              /* Plugin flag*/
     0xFFFFFFFF                /* empty - extra data word */
 };
diff --git a/ports/mimxrt10xx/boards/teensy40/flash_config.c b/ports/mimxrt10xx/boards/teensy40/flash_config.c
index 3f4ab0271d..d878124b40 100644
--- a/ports/mimxrt10xx/boards/teensy40/flash_config.c
+++ b/ports/mimxrt10xx/boards/teensy40/flash_config.c
@@ -15,7 +15,7 @@ __attribute__((section(".boot_hdr.ivt")))
  *  IVT Data
  *************************************/
 const ivt image_vector_table = {
-    IVT_HEADER,                       /* IVT Header */
+    0x432000D1,                       /* Teensy bootloader looks for this value*/
     IMAGE_ENTRY_ADDRESS,              /* Image Entry Function */
     IVT_RSVD,                         /* Reserved = 0 */
     (uint32_t)DCD_ADDRESS,            /* Address where DCD information is stored */
@@ -25,13 +25,15 @@ const ivt image_vector_table = {
     IVT_RSVD                          /* Reserved = 0 */
 };
 
+extern unsigned long _flashimagelen;
+
 __attribute__((section(".boot_hdr.boot_data")))
 /*************************************
  *  Boot Data
  *************************************/
 const BOOT_DATA_T boot_data = {
     FLASH_BASE,               /* boot start location */
-    FLASH_SIZE,               /* size */
+    (uint32_t)&_flashimagelen, /* actual size of image */
     PLUGIN_FLAG,              /* Plugin flag*/
     0xFFFFFFFF                /* empty - extra data word */
 };
diff --git a/ports/mimxrt10xx/boards/teensy41/flash_config.c b/ports/mimxrt10xx/boards/teensy41/flash_config.c
index 09886dece6..e0f5a5bd7d 100644
--- a/ports/mimxrt10xx/boards/teensy41/flash_config.c
+++ b/ports/mimxrt10xx/boards/teensy41/flash_config.c
@@ -15,7 +15,7 @@ __attribute__((section(".boot_hdr.ivt")))
  *  IVT Data
  *************************************/
 const ivt image_vector_table = {
-    IVT_HEADER,                       /* IVT Header */
+    0x432000D1,                       /* Teensy bootloader looks for this value*/
     IMAGE_ENTRY_ADDRESS,              /* Image Entry Function */
     IVT_RSVD,                         /* Reserved = 0 */
     (uint32_t)DCD_ADDRESS,            /* Address where DCD information is stored */
@@ -25,13 +25,15 @@ const ivt image_vector_table = {
     IVT_RSVD                          /* Reserved = 0 */
 };
 
+extern unsigned long _flashimagelen;
+
 __attribute__((section(".boot_hdr.boot_data")))
 /*************************************
  *  Boot Data
  *************************************/
 const BOOT_DATA_T boot_data = {
     FLASH_BASE,               /* boot start location */
-    FLASH_SIZE,               /* size */
+    (uint32_t)&_flashimagelen, /* actual size of image */
     PLUGIN_FLAG,              /* Plugin flag*/
     0xFFFFFFFF                /* empty - extra data word */
 };
diff --git a/ports/mimxrt10xx/linking/common.ld b/ports/mimxrt10xx/linking/common.ld
index 44e8d537c4..b6f1acc8d0 100644
--- a/ports/mimxrt10xx/linking/common.ld
+++ b/ports/mimxrt10xx/linking/common.ld
@@ -74,7 +74,6 @@ SECTIONS
         _etext = .;        /* define a global symbol at end of code */
         __etext = .;       /* define a global symbol at end of code */
     } > FLASH_FIRMWARE
-
     _ld_filesystem_start = ORIGIN(FLASH_FATFS);
     _ld_filesystem_end = _ld_filesystem_start + LENGTH(FLASH_FATFS);
 
@@ -127,6 +126,8 @@ SECTIONS
     _ld_dtcm_data_flash_copy = LOADADDR(.dtcm_data);
     _ld_dtcm_data_size = SIZEOF(.dtcm_data);
 
+    _flashimagelen = _ld_dtcm_data_flash_copy + _ld_dtcm_data_size - flash_config_location;
+
     .dtcm_bss :
     {
         . = ALIGN(4);