diff --git a/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/TOOLCHAIN_IAR/TARGET_MCU_NORDIC_16K/nRF51822_QFAA.icf b/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/TOOLCHAIN_IAR/TARGET_MCU_NORDIC_16K/nRF51822_QFAA.icf
index 22e3abd0be..d71c75cb3f 100644
--- a/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/TOOLCHAIN_IAR/TARGET_MCU_NORDIC_16K/nRF51822_QFAA.icf
+++ b/libraries/mbed/targets/cmsis/TARGET_NORDIC/TARGET_MCU_NRF51822/TOOLCHAIN_IAR/TARGET_MCU_NORDIC_16K/nRF51822_QFAA.icf
@@ -9,8 +9,8 @@ define symbol __ICFEDIT_region_ROM_end__   = 0x0003FFFF;
 define symbol __ICFEDIT_region_RAM_start__ = 0x20002000;
 define symbol __ICFEDIT_region_RAM_end__   = 0x20003FFF;
 /*-Sizes-*/
-define symbol __ICFEDIT_size_cstack__ = 0x800;
-define symbol __ICFEDIT_size_heap__   = 0xF00;
+define symbol __ICFEDIT_size_cstack__ = 0x400;
+define symbol __ICFEDIT_size_heap__   = 0x900;
 /**** End of ICF editor section. ###ICF###*/
 
 define symbol __code_start_soft_device__ = 0x0;