diff --git a/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.cpp b/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.cpp
index cc1064628b..eb31c5ed9f 100644
--- a/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.cpp
+++ b/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.cpp
@@ -13,7 +13,7 @@
    You can override this function in your code to reserve a number of bytes
    for the stack.
 */
-extern "C" WEAK uint32_t __reserved_stack_size();
-extern "C" WEAK uint32_t __reserved_stack_size() {
+extern "C" __attribute__((weak)) uint32_t __reserved_stack_size();
+extern "C" __attribute__((weak)) uint32_t __reserved_stack_size() {
     return 0; // return 0 to indicate that nothing is reserved
 }
diff --git a/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.h b/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.h
index 3fda8f5e30..4ba0770b4f 100644
--- a/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.h
+++ b/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC408X/TOOLCHAIN_ARM_STD/sys_helper.h
@@ -2,7 +2,6 @@
 #define SYS_HELPER_H
 
 #include <stdint.h>
-#include "toolchain.h"
 
 #ifdef __cplusplus
 extern "C" {