diff --git a/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_GR_LYCHEE/device/os_tick_ostm.c b/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_GR_LYCHEE/device/os_tick_ostm.c
index e28da960e7..89420e51f2 100644
--- a/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_GR_LYCHEE/device/os_tick_ostm.c
+++ b/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_GR_LYCHEE/device/os_tick_ostm.c
@@ -131,7 +131,7 @@ int32_t OS_Tick_Setup (uint32_t freq, IRQHandler_t handler)
 }
 
 /// Enable OS Tick.
-int32_t  OS_Tick_Enable (void)
+void  OS_Tick_Enable (void)
 {
 
   if (OSTM_PendIRQ != 0U) {
@@ -141,12 +141,10 @@ int32_t  OS_Tick_Enable (void)
 
   // Start the OSTM counter
   OSTM.OSTMnTS = 0x01U;
-
-  return (0);
 }
 
 /// Disable OS Tick.
-int32_t  OS_Tick_Disable (void) {
+void  OS_Tick_Disable (void) {
 
   // Stop the OSTM counter
   OSTM.OSTMnTT = 0x01U;
@@ -155,14 +153,12 @@ int32_t  OS_Tick_Disable (void) {
     IRQ_ClearPending (OSTM_IRQn);
     OSTM_PendIRQ = 1U;
   }
-
-  return (0);
 }
 
 // Acknowledge OS Tick IRQ.
-int32_t OS_Tick_AcknowledgeIRQ (void)
+void OS_Tick_AcknowledgeIRQ (void)
 {
-  return (IRQ_ClearPending (OSTM_IRQn));
+  IRQ_ClearPending (OSTM_IRQn);
 }
 
 // Get OS Tick IRQ number.
diff --git a/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_RZ_A1H/device/os_tick_ostm.c b/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_RZ_A1H/device/os_tick_ostm.c
index f1983402b7..30b830d584 100644
--- a/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_RZ_A1H/device/os_tick_ostm.c
+++ b/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_RZ_A1H/device/os_tick_ostm.c
@@ -131,7 +131,7 @@ int32_t OS_Tick_Setup (uint32_t freq, IRQHandler_t handler)
 }
 
 /// Enable OS Tick.
-int32_t  OS_Tick_Enable (void)
+void  OS_Tick_Enable (void)
 {
 
   if (OSTM_PendIRQ != 0U) {
@@ -141,12 +141,10 @@ int32_t  OS_Tick_Enable (void)
 
   // Start the OSTM counter
   OSTM.OSTMnTS = 0x01U;
-
-  return (0);
 }
 
 /// Disable OS Tick.
-int32_t  OS_Tick_Disable (void)
+void  OS_Tick_Disable (void)
 {
 
   // Stop the OSTM counter
@@ -156,14 +154,12 @@ int32_t  OS_Tick_Disable (void)
     IRQ_ClearPending (OSTM_IRQn);
     OSTM_PendIRQ = 1U;
   }
-
-  return (0);
 }
 
 // Acknowledge OS Tick IRQ.
-int32_t OS_Tick_AcknowledgeIRQ (void)
+void  OS_Tick_AcknowledgeIRQ (void)
 {
-  return (IRQ_ClearPending (OSTM_IRQn));
+  IRQ_ClearPending (OSTM_IRQn);
 }
 
 // Get OS Tick IRQ number.
diff --git a/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_VK_RZ_A1H/device/os_tick_ostm.c b/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_VK_RZ_A1H/device/os_tick_ostm.c
index e5b259184a..830b407fcd 100644
--- a/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_VK_RZ_A1H/device/os_tick_ostm.c
+++ b/targets/TARGET_RENESAS/TARGET_RZ_A1XX/TARGET_VK_RZ_A1H/device/os_tick_ostm.c
@@ -131,7 +131,7 @@ int32_t OS_Tick_Setup (uint32_t freq, IRQHandler_t handler)
 }
 
 /// Enable OS Tick.
-int32_t  OS_Tick_Enable (void)
+void  OS_Tick_Enable (void)
 {
 
   if (OSTM_PendIRQ != 0U) {
@@ -141,12 +141,10 @@ int32_t  OS_Tick_Enable (void)
 
   // Start the OSTM counter
   OSTM.OSTMnTS = 0x01U;
-
-  return (0);
 }
 
 /// Disable OS Tick.
-int32_t  OS_Tick_Disable (void)
+void  OS_Tick_Disable (void)
 {
 
   // Stop the OSTM counter
@@ -156,14 +154,12 @@ int32_t  OS_Tick_Disable (void)
     IRQ_ClearPending (OSTM_IRQn);
     OSTM_PendIRQ = 1U;
   }
-
-  return (0);
 }
 
 // Acknowledge OS Tick IRQ.
-int32_t OS_Tick_AcknowledgeIRQ (void)
+void  OS_Tick_AcknowledgeIRQ (void)
 {
-  return (IRQ_ClearPending (OSTM_IRQn));
+  IRQ_ClearPending (OSTM_IRQn);
 }
 
 // Get OS Tick IRQ number.
diff --git a/targets/TARGET_RENESAS/mbed_rtx.h b/targets/TARGET_RENESAS/mbed_rtx.h
index f7c91c6a21..c8eba52d14 100644
--- a/targets/TARGET_RENESAS/mbed_rtx.h
+++ b/targets/TARGET_RENESAS/mbed_rtx.h
@@ -19,7 +19,6 @@
 #include <stdint.h>
 
 #if defined(TARGET_RZ_A1H) || defined(TARGET_VK_RZ_A1H) || defined(TARGET_GR_LYCHEE)
-#define OS_IDLE_THREAD_STACK_SIZE   512
 
 #if defined(__CC_ARM)
     extern char Image$$ARM_LIB_STACK$$Base[];
diff --git a/targets/TARGET_STM/mbed_rtx.h b/targets/TARGET_STM/mbed_rtx.h
index dc5c8d8d6b..d323e3b973 100644
--- a/targets/TARGET_STM/mbed_rtx.h
+++ b/targets/TARGET_STM/mbed_rtx.h
@@ -17,6 +17,8 @@
 #ifndef MBED_MBED_RTX_H
 #define MBED_MBED_RTX_H
 
+#include <stdint.h>
+
 #ifndef INITIAL_SP
 
 #if (defined(TARGET_STM32L475VG) ||\