diff --git a/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/device/TOOLCHAIN_IAR/stm32l475xx.icf b/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/device/TOOLCHAIN_IAR/stm32l475xx.icf
index 0ea0b53a05..2c76cd5995 100644
--- a/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/device/TOOLCHAIN_IAR/stm32l475xx.icf
+++ b/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/device/TOOLCHAIN_IAR/stm32l475xx.icf
@@ -10,7 +10,9 @@ define symbol __region_ROM_end__   = MBED_APP_START + MBED_APP_SIZE - 1;
 /* Vector table dynamic copy: Total: 98 vectors * 4 = 392 bytes (0x188) to be reserved in RAM */
 define symbol __NVIC_start__          = 0x10000000;
 define symbol __NVIC_end__            = 0x10000187;
-define symbol __region_SRAM2_start__  = 0x10000188;
+define symbol __region_CSTACK_start__  = 0x10000188;
+define symbol __region_CSTACK_end__    = __region_CSTACK_start__ + MBED_BOOT_STACK_SIZE;
+define symbol __region_SRAM2_start__  = __region_CSTACK_end__;
 define symbol __region_SRAM2_end__    = 0x10007FFF;
 define symbol __region_CRASH_DATA_RAM_start__  = 0x20000000;
 define symbol __region_CRASH_DATA_RAM_end__  = 0x200000FF;
@@ -20,9 +22,10 @@ define symbol __region_SRAM1_end__    = 0x20017FFF;
 /* Memory regions */
 define memory mem with size = 4G;
 define region ROM_region = mem:[from __region_ROM_start__ to __region_ROM_end__];
-define region SRAM2_region = mem:[from __region_SRAM2_start__ to __region_SRAM2_end__];
+define region CSTACK_region = mem:[from __region_CSTACK_start__ to __region_CSTACK_end__];
 define region CRASH_DATA_RAM_region = mem:[from __region_CRASH_DATA_RAM_start__ to __region_CRASH_DATA_RAM_end__];
-define region SRAM1_region = mem:[from __region_SRAM1_start__ to __region_SRAM1_end__];
+define region RAM_region = mem:[from __region_SRAM2_start__ to __region_SRAM2_end__]
+                          | mem:[from __region_SRAM1_start__ to __region_SRAM1_end__];
 
 /* Define Crash Data Symbols */
 define exported symbol __CRASH_DATA_RAM_START__ = __region_CRASH_DATA_RAM_start__;
@@ -33,9 +36,9 @@ if (!isdefinedsymbol(MBED_BOOT_STACK_SIZE)) {
 }
 
 define symbol __size_cstack__ = MBED_BOOT_STACK_SIZE;
-define symbol __size_heap__   = 0x17000;
+define symbol __size_heap__   = 0x10000;
 define block CSTACK    with alignment = 8, size = __size_cstack__   { };
-define block HEAP      with alignment = 8, size = __size_heap__     { };
+define block HEAP      with expanding size, alignment = 8, minimum size = __size_heap__     { };
 
 initialize by copy with packing = zeros { readwrite };
 do not initialize  { section .noinit };
@@ -43,5 +46,5 @@ do not initialize  { section .noinit };
 place at address mem:__intvec_start__ { readonly section .intvec };
 
 place in ROM_region   { readonly };
-place in SRAM1_region { readwrite, block HEAP };
-place in SRAM2_region { first block CSTACK, zeroinit };
+place in CSTACK_region { block CSTACK };
+place in RAM_region                     { block HEAP, readwrite, zeroinit };
diff --git a/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L476xG/device/TOOLCHAIN_IAR/stm32l476xx.icf b/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L476xG/device/TOOLCHAIN_IAR/stm32l476xx.icf
index 864e944e7b..2c76cd5995 100644
--- a/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L476xG/device/TOOLCHAIN_IAR/stm32l476xx.icf
+++ b/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L476xG/device/TOOLCHAIN_IAR/stm32l476xx.icf
@@ -10,7 +10,9 @@ define symbol __region_ROM_end__   = MBED_APP_START + MBED_APP_SIZE - 1;
 /* Vector table dynamic copy: Total: 98 vectors * 4 = 392 bytes (0x188) to be reserved in RAM */
 define symbol __NVIC_start__          = 0x10000000;
 define symbol __NVIC_end__            = 0x10000187;
-define symbol __region_SRAM2_start__  = 0x10000188;
+define symbol __region_CSTACK_start__  = 0x10000188;
+define symbol __region_CSTACK_end__    = __region_CSTACK_start__ + MBED_BOOT_STACK_SIZE;
+define symbol __region_SRAM2_start__  = __region_CSTACK_end__;
 define symbol __region_SRAM2_end__    = 0x10007FFF;
 define symbol __region_CRASH_DATA_RAM_start__  = 0x20000000;
 define symbol __region_CRASH_DATA_RAM_end__  = 0x200000FF;
@@ -20,9 +22,10 @@ define symbol __region_SRAM1_end__    = 0x20017FFF;
 /* Memory regions */
 define memory mem with size = 4G;
 define region ROM_region = mem:[from __region_ROM_start__ to __region_ROM_end__];
-define region SRAM2_region = mem:[from __region_SRAM2_start__ to __region_SRAM2_end__];
+define region CSTACK_region = mem:[from __region_CSTACK_start__ to __region_CSTACK_end__];
 define region CRASH_DATA_RAM_region = mem:[from __region_CRASH_DATA_RAM_start__ to __region_CRASH_DATA_RAM_end__];
-define region SRAM1_region = mem:[from __region_SRAM1_start__ to __region_SRAM1_end__];
+define region RAM_region = mem:[from __region_SRAM2_start__ to __region_SRAM2_end__]
+                          | mem:[from __region_SRAM1_start__ to __region_SRAM1_end__];
 
 /* Define Crash Data Symbols */
 define exported symbol __CRASH_DATA_RAM_START__ = __region_CRASH_DATA_RAM_start__;
@@ -35,7 +38,7 @@ if (!isdefinedsymbol(MBED_BOOT_STACK_SIZE)) {
 define symbol __size_cstack__ = MBED_BOOT_STACK_SIZE;
 define symbol __size_heap__   = 0x10000;
 define block CSTACK    with alignment = 8, size = __size_cstack__   { };
-define block HEAP      with alignment = 8, size = __size_heap__     { };
+define block HEAP      with expanding size, alignment = 8, minimum size = __size_heap__     { };
 
 initialize by copy with packing = zeros { readwrite };
 do not initialize  { section .noinit };
@@ -43,5 +46,5 @@ do not initialize  { section .noinit };
 place at address mem:__intvec_start__ { readonly section .intvec };
 
 place in ROM_region   { readonly };
-place in SRAM1_region { readwrite, block HEAP };
-place in SRAM2_region { block CSTACK };
+place in CSTACK_region { block CSTACK };
+place in RAM_region                     { block HEAP, readwrite, zeroinit };
diff --git a/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L486xG/device/TOOLCHAIN_IAR/stm32l486xx.icf b/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L486xG/device/TOOLCHAIN_IAR/stm32l486xx.icf
index 864e944e7b..2c76cd5995 100644
--- a/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L486xG/device/TOOLCHAIN_IAR/stm32l486xx.icf
+++ b/targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L486xG/device/TOOLCHAIN_IAR/stm32l486xx.icf
@@ -10,7 +10,9 @@ define symbol __region_ROM_end__   = MBED_APP_START + MBED_APP_SIZE - 1;
 /* Vector table dynamic copy: Total: 98 vectors * 4 = 392 bytes (0x188) to be reserved in RAM */
 define symbol __NVIC_start__          = 0x10000000;
 define symbol __NVIC_end__            = 0x10000187;
-define symbol __region_SRAM2_start__  = 0x10000188;
+define symbol __region_CSTACK_start__  = 0x10000188;
+define symbol __region_CSTACK_end__    = __region_CSTACK_start__ + MBED_BOOT_STACK_SIZE;
+define symbol __region_SRAM2_start__  = __region_CSTACK_end__;
 define symbol __region_SRAM2_end__    = 0x10007FFF;
 define symbol __region_CRASH_DATA_RAM_start__  = 0x20000000;
 define symbol __region_CRASH_DATA_RAM_end__  = 0x200000FF;
@@ -20,9 +22,10 @@ define symbol __region_SRAM1_end__    = 0x20017FFF;
 /* Memory regions */
 define memory mem with size = 4G;
 define region ROM_region = mem:[from __region_ROM_start__ to __region_ROM_end__];
-define region SRAM2_region = mem:[from __region_SRAM2_start__ to __region_SRAM2_end__];
+define region CSTACK_region = mem:[from __region_CSTACK_start__ to __region_CSTACK_end__];
 define region CRASH_DATA_RAM_region = mem:[from __region_CRASH_DATA_RAM_start__ to __region_CRASH_DATA_RAM_end__];
-define region SRAM1_region = mem:[from __region_SRAM1_start__ to __region_SRAM1_end__];
+define region RAM_region = mem:[from __region_SRAM2_start__ to __region_SRAM2_end__]
+                          | mem:[from __region_SRAM1_start__ to __region_SRAM1_end__];
 
 /* Define Crash Data Symbols */
 define exported symbol __CRASH_DATA_RAM_START__ = __region_CRASH_DATA_RAM_start__;
@@ -35,7 +38,7 @@ if (!isdefinedsymbol(MBED_BOOT_STACK_SIZE)) {
 define symbol __size_cstack__ = MBED_BOOT_STACK_SIZE;
 define symbol __size_heap__   = 0x10000;
 define block CSTACK    with alignment = 8, size = __size_cstack__   { };
-define block HEAP      with alignment = 8, size = __size_heap__     { };
+define block HEAP      with expanding size, alignment = 8, minimum size = __size_heap__     { };
 
 initialize by copy with packing = zeros { readwrite };
 do not initialize  { section .noinit };
@@ -43,5 +46,5 @@ do not initialize  { section .noinit };
 place at address mem:__intvec_start__ { readonly section .intvec };
 
 place in ROM_region   { readonly };
-place in SRAM1_region { readwrite, block HEAP };
-place in SRAM2_region { block CSTACK };
+place in CSTACK_region { block CSTACK };
+place in RAM_region                     { block HEAP, readwrite, zeroinit };