diff --git a/rtos/TARGET_CORTEX/mbed_rtx_conf.h b/rtos/TARGET_CORTEX/mbed_rtx_conf.h
index f0b2fc3984..8554098e24 100644
--- a/rtos/TARGET_CORTEX/mbed_rtx_conf.h
+++ b/rtos/TARGET_CORTEX/mbed_rtx_conf.h
@@ -39,10 +39,16 @@
 #define OS_TIMER_THREAD_STACK_SIZE  MBED_CONF_RTOS_TIMER_THREAD_STACK_SIZE
 #endif
 
-#ifdef MBED_CONF_APP_IDLE_THREAD_STACK_SIZE
-#define OS_IDLE_THREAD_STACK_SIZE   MBED_CONF_APP_IDLE_THREAD_STACK_SIZE
+// Increase the idle thread stack size when tickless is enabled
+#if defined(MBED_TICKLESS) && defined(LPTICKER_DELAY_TICKS) && (LPTICKER_DELAY_TICKS > 0)
+#define EXTRA_IDLE_STACK MBED_CONF_RTOS_IDLE_THREAD_STACK_SIZE_TICKLESS_EXTRA
 #else
-#define OS_IDLE_THREAD_STACK_SIZE   MBED_CONF_RTOS_IDLE_THREAD_STACK_SIZE
+#define EXTRA_IDLE_STACK 0
+#endif
+#ifdef MBED_CONF_APP_IDLE_THREAD_STACK_SIZE
+#define OS_IDLE_THREAD_STACK_SIZE   (MBED_CONF_APP_IDLE_THREAD_STACK_SIZE + EXTRA_IDLE_STACK)
+#else
+#define OS_IDLE_THREAD_STACK_SIZE   (MBED_CONF_RTOS_IDLE_THREAD_STACK_SIZE + EXTRA_IDLE_STACK)
 #endif
 
 #define OS_DYNAMIC_MEM_SIZE         0
diff --git a/rtos/mbed_lib.json b/rtos/mbed_lib.json
index 7714cdd743..4f75ee88df 100644
--- a/rtos/mbed_lib.json
+++ b/rtos/mbed_lib.json
@@ -17,6 +17,10 @@
          "thread-stack-size": {
             "help": "The default stack size of new threads",
             "value": 4096
+         },
+         "idle-thread-stack-size-tickless-extra": {
+            "help": "Additional size to add to the idle thread when tickless is enabled and LPTICKER_DELAY_TICKS is used",
+            "value": 256
          }
     },
     "macros": ["_RTE_"]