diff --git a/targets/TARGET_STM/mbed_rtx.h b/targets/TARGET_STM/mbed_rtx.h
index 0569e60b56..39c29e7060 100644
--- a/targets/TARGET_STM/mbed_rtx.h
+++ b/targets/TARGET_STM/mbed_rtx.h
@@ -102,7 +102,8 @@
 #elif (defined(TARGET_STM32F429ZI) ||\
        defined(TARGET_STM32F437VG) ||\
        defined(TARGET_STM32F439VI) ||\
-       defined(TARGET_STM32F439ZI))
+       defined(TARGET_STM32F439ZI) ||\
+       defined(TARGET_STM32WB55RG))
 #define INITIAL_SP              (0x20030000UL)
 
 #elif defined(TARGET_STM32F412ZG)