diff --git a/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC15XX/TOOLCHAIN_ARM_MICRO/startup_LPC15xx.s b/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC15XX/TOOLCHAIN_ARM_MICRO/startup_LPC15xx.s
index 0cd13c72ae..0c9e87ff3c 100644
--- a/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC15XX/TOOLCHAIN_ARM_MICRO/startup_LPC15xx.s
+++ b/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC15XX/TOOLCHAIN_ARM_MICRO/startup_LPC15xx.s
@@ -31,8 +31,9 @@
 Stack_Size      EQU     0x00000200
 
                 AREA    STACK, NOINIT, READWRITE, ALIGN=3
-Stack_Mem       SPACE   Stack_Size
-__initial_sp
+                EXPORT  __initial_sp
+
+__initial_sp        EQU     0x02009000  ; Top of RAM from LPC1549
 
 
 ; <h> Heap Configuration