diff --git a/core/cortex-m/task.c b/core/cortex-m/task.c
index aaaa776385..41b0b7e39a 100644
--- a/core/cortex-m/task.c
+++ b/core/cortex-m/task.c
@@ -129,6 +129,8 @@ static int need_resched_or_profiling = 0;
  */
 static uint32_t tasks_ready = (1<<TASK_ID_COUNT) - 1;
 
+static int start_called;  /* Has task swapping started */
+
 
 static task_ *__get_current(void)
 {
@@ -211,6 +213,12 @@ uint32_t *task_get_event_bitmap(task_id_t tskid)
 }
 
 
+int task_start_called(void)
+{
+	return start_called;
+}
+
+
 /* Scheduling system call */
 void svc_handler(int desched, task_id_t resched)
 {
@@ -597,6 +605,7 @@ int task_start(void)
 #ifdef CONFIG_TASK_PROFILING
 	task_start_time = exc_end_time = get_time().val;
 #endif
+	start_called = 1;
 
 	return __task_start(&need_resched_or_profiling);
 }
diff --git a/core/cortex-m/timer.c b/core/cortex-m/timer.c
index 14e59c900f..994f9c1245 100644
--- a/core/cortex-m/timer.c
+++ b/core/cortex-m/timer.c
@@ -138,6 +138,13 @@ int timer_cancel(task_id_t tskid)
 void usleep(unsigned us)
 {
 	uint32_t evt = 0;
+
+	/* If task scheduling has not started, just delay */
+	if (!task_start_called()) {
+		udelay(us);
+		return;
+	}
+
 	ASSERT(us);
 	do {
 		evt |= task_wait_event(us);
diff --git a/include/task.h b/include/task.h
index 660195460e..075ed43698 100644
--- a/include/task.h
+++ b/include/task.h
@@ -99,22 +99,26 @@ void task_start_irq_handler(void *excep_return);
  * last call of the interrupt handler. */
 void task_resched_if_needed(void *excep_return);
 
-/* Initializes tasks and interrupt controller. */
+/* Initialize tasks and interrupt controller. */
 int task_pre_init(void);
 
-/* Starts task scheduling.  Does not normally return. */
+/* Start task scheduling.  Does not normally return. */
 int task_start(void);
 
-/* Enables an interrupt. */
+/* Return non-zero if task_start() has been called and task scheduling has
+ * started. */
+int task_start_called(void);
+
+/* Enable an interrupt. */
 void task_enable_irq(int irq);
 
-/* Disables an interrupt. */
+/* Disable an interrupt. */
 void task_disable_irq(int irq);
 
-/* Software-triggers an interrupt. */
+/* Software-trigger an interrupt. */
 void task_trigger_irq(int irq);
 
-/* Clears a pending interrupt.
+/* Clear a pending interrupt.
  *
  * Note that most interrupts can be removed from the pending state simply by
  * handling whatever caused the interrupt in the first place.  This only needs