diff --git a/rtos/TARGET_CORTEX/TOOLCHAIN_IAR/mbed_boot_iar.c b/rtos/TARGET_CORTEX/TOOLCHAIN_IAR/mbed_boot_iar.c
index 0812be93f0..8659355fa3 100644
--- a/rtos/TARGET_CORTEX/TOOLCHAIN_IAR/mbed_boot_iar.c
+++ b/rtos/TARGET_CORTEX/TOOLCHAIN_IAR/mbed_boot_iar.c
@@ -87,7 +87,7 @@ void __iar_program_start(void)
 
 void mbed_toolchain_init(void)
 {
-#if defined(__IAR_SYSTEMS_ICC__ ) && (__VER__ >= 8000000)
+#if defined(__IAR_SYSTEMS_ICC__ ) && (__VER__ >= 8000000) && !defined(MBED_RTOS_SINGLE_THREAD)
     __iar_Initlocks();
 #endif