diff --git a/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp b/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp
index 9ea0282b79..d359ce3e12 100644
--- a/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp
@@ -21,8 +21,8 @@
     #define STACK_SIZE DEFAULT_STACK_SIZE/8
 #elif defined(TARGET_STM32F334R8) && (defined(TOOLCHAIN_GCC) || defined(TOOLCHAIN_IAR))
     #define STACK_SIZE DEFAULT_STACK_SIZE/4
-#elif defined(TARGET_STM32F103RB) && defined(TOOLCHAIN_IAR)
-    #define STACK_SIZE DEFAULT_STACK_SIZE/4
+#elif defined(TARGET_STM32F103RB)
+    #define STACK_SIZE DEFAULT_STACK_SIZE/2
 #elif defined(TARGET_STM32F030R8) && defined(TOOLCHAIN_IAR)
     #define STACK_SIZE DEFAULT_STACK_SIZE/4	
 #elif defined(TARGET_STM32F070RB)
diff --git a/TESTS/mbedmicro-rtos-mbed/threads/main.cpp b/TESTS/mbedmicro-rtos-mbed/threads/main.cpp
index be0b3cd5ff..82b074c9cc 100644
--- a/TESTS/mbedmicro-rtos-mbed/threads/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/threads/main.cpp
@@ -17,7 +17,7 @@
  */
 #if defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
     #define STACK_SIZE 512
-#elif (defined(TARGET_STM32F070RB) || defined(TARGET_STM32F072RB))
+#elif (defined(TARGET_STM32F070RB) || defined(TARGET_STM32F072RB) || defined(TARGET_STM32F103RB))
     #define STACK_SIZE 512
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
diff --git a/rtos/rtx/TARGET_CORTEX_M/RTX_CM_lib.h b/rtos/rtx/TARGET_CORTEX_M/RTX_CM_lib.h
index f91cfeedd2..e2468fbfc4 100644
--- a/rtos/rtx/TARGET_CORTEX_M/RTX_CM_lib.h
+++ b/rtos/rtx/TARGET_CORTEX_M/RTX_CM_lib.h
@@ -353,7 +353,8 @@ extern void pre_main (void);
 
 #if defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832) || defined (TARGET_STM32F334R8) ||\
     defined(TARGET_STM32F070RB) || defined(TARGET_STM32F072RB) || \
-    defined(TARGET_STM32F302R8) || defined(TARGET_STM32F303K8) || defined (TARGET_STM32F334C8)
+    defined(TARGET_STM32F302R8) || defined(TARGET_STM32F303K8) || defined (TARGET_STM32F334C8) ||\
+    defined(TARGET_STM32F103RB)
 static uint32_t thread_stack_main[DEFAULT_STACK_SIZE / sizeof(uint32_t)];
 #else
 static uint32_t thread_stack_main[DEFAULT_STACK_SIZE * 2 / sizeof(uint32_t)];