diff --git a/include/metalsvm/tasks_types.h b/include/metalsvm/tasks_types.h
index 214df8e7..784167a7 100644
--- a/include/metalsvm/tasks_types.h
+++ b/include/metalsvm/tasks_types.h
@@ -40,7 +40,7 @@
 extern "C" {
 #endif
 
-#define MAX_PRIO 	32
+#define MAX_PRIO 	31
 #define REALTIME_PRIO	31
 #define HIGH_PRIO	16
 #define NORMAL_PRIO	8
diff --git a/kernel/tasks.c b/kernel/tasks.c
index cf16ef40..115f5be9 100644
--- a/kernel/tasks.c
+++ b/kernel/tasks.c
@@ -129,13 +129,13 @@ static void finish_task_switch(void)
 	spinlock_lock(&runqueues[core_id].lock);
 	if ((old = runqueues[core_id].old_task) != NULL) {
 		prio = old->prio;
-		if (!runqueues[core_id].queue[prio].first) {
+		if (!runqueues[core_id].queue[prio-1].first) {
 			old->prev = NULL;
-			runqueues[core_id].queue[prio].first = runqueues[core_id].queue[prio].last = old;
+			runqueues[core_id].queue[prio-1].first = runqueues[core_id].queue[prio-1].last = old;
 		} else {
-			old->prev = runqueues[core_id].queue[prio].last;
-			runqueues[core_id].queue[prio].last->next = old;
-			runqueues[core_id].queue[prio].last = old;
+			old->prev = runqueues[core_id].queue[prio-1].last;
+			runqueues[core_id].queue[prio-1].last->next = old;
+			runqueues[core_id].queue[prio-1].last = old;
 		}
 		runqueues[core_id].old_task = NULL;
 		runqueues[core_id].prio_bitmap |= (1 << prio);
@@ -242,7 +242,7 @@ static int create_task(tid_t* id, internal_entry_point_t ep, void* arg, uint8_t
 		return -EINVAL;
 	if (BUILTIN_EXPECT(prio == IDLE_PRIO, 0))
 		return -EINVAL;
-	if (BUILTIN_EXPECT(prio >= MAX_PRIO, 0))
+	if (BUILTIN_EXPECT(prio > MAX_PRIO, 0))
 		return -EINVAL;
 
 	spinlock_irqsave_lock(&table_lock);
@@ -282,15 +282,22 @@ static int create_task(tid_t* id, internal_entry_point_t ep, void* arg, uint8_t
 			// add task in the runqueue
 			spinlock_lock(&runqueues[core_id].lock);
 			runqueues[core_id].prio_bitmap |= (1 << prio);
-			if (!runqueues[core_id].queue[prio].first) {
+			kprintf("prio %d %p\n", prio, runqueues[core_id].queue[prio-1].first);
+			if (!runqueues[core_id].queue[prio-1].first) {
 				task_table[i].prev = NULL;
-				runqueues[core_id].queue[prio].first = task_table+i;
-				runqueues[core_id].queue[prio].last = task_table+i;
+				kputs("A");
+				runqueues[core_id].queue[prio-1].first = task_table+i;
+				kputs("B");
+				runqueues[core_id].queue[prio-1].last = task_table+i;
+				kputs("C");
 				task_table[i].next = NULL;
 			} else {
-				task_table[i].prev = runqueues[core_id].queue[prio].last;
-				runqueues[core_id].queue[prio].last->next = task_table+i;
-				runqueues[core_id].queue[prio].last = task_table+i;
+				kputs("D");
+				task_table[i].prev = runqueues[core_id].queue[prio-1].last;
+				kputs("E");
+				runqueues[core_id].queue[prio-1].last->next = task_table+i;
+				kputs("F");
+				runqueues[core_id].queue[prio-1].last = task_table+i;
 				task_table[i].next = NULL;
 			}
 			spinlock_unlock(&runqueues[core_id].lock);
@@ -364,15 +371,15 @@ int sys_fork(void)
 			// add task in the runqueue
 			spinlock_lock(&runqueues[core_id].lock);
 			runqueues[core_id].prio_bitmap |= (1 << parent_task->prio);
-			if (!runqueues[core_id].queue[parent_task->prio].first) {
+			if (!runqueues[core_id].queue[parent_task->prio-1].first) {
 				task_table[i].prev = NULL;
-				runqueues[core_id].queue[parent_task->prio].first = task_table+i;
-				runqueues[core_id].queue[parent_task->prio].last = task_table+i;
+				runqueues[core_id].queue[parent_task->prio-1].first = task_table+i;
+				runqueues[core_id].queue[parent_task->prio-1].last = task_table+i;
 				task_table[i].next = NULL;
 			} else {
-				task_table[i].prev = runqueues[core_id].queue[parent_task->prio].last;
-				runqueues[core_id].queue[parent_task->prio].last->next = task_table+i;
-				runqueues[core_id].queue[parent_task->prio].last = task_table+i;
+				task_table[i].prev = runqueues[core_id].queue[parent_task->prio-1].last;
+				runqueues[core_id].queue[parent_task->prio-1].last->next = task_table+i;
+				runqueues[core_id].queue[parent_task->prio-1].last = task_table+i;
 				task_table[i].next = NULL;
 			}
 			spinlock_unlock(&runqueues[core_id].lock);
@@ -442,7 +449,7 @@ int create_kernel_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio)
 	kernel_args->func = ep;
 	kernel_args->args = args;
 
-	if (prio >= MAX_PRIO)
+	if (prio > MAX_PRIO)
 		prio = NORMAL_PRIO;
 
 	return create_task(id, kernel_entry, kernel_args, prio);
@@ -861,15 +868,15 @@ int wakeup_task(tid_t id)
 
 		spinlock_lock(&runqueues[core_id].lock);
 		// add task to the runqueue
-		if (!runqueues[core_id].queue[prio].last) {
-			runqueues[core_id].queue[prio].last = runqueues[core_id].queue[prio].first = task;
+		if (!runqueues[core_id].queue[prio-1].last) {
+			runqueues[core_id].queue[prio-1].last = runqueues[core_id].queue[prio-1].first = task;
 			task->next = task->prev = NULL;
 			runqueues[core_id].prio_bitmap |= (1 << prio);
 		} else {
-			task->prev = runqueues[core_id].queue[prio].last;
+			task->prev = runqueues[core_id].queue[prio-1].last;
 			task->next = NULL;
-			runqueues[core_id].queue[prio].last->next = task;
-			runqueues[core_id].queue[prio].last = task;
+			runqueues[core_id].queue[prio-1].last->next = task;
+			runqueues[core_id].queue[prio-1].last = task;
 		}
 		spinlock_unlock(&runqueues[core_id].lock);
 	}
@@ -913,16 +920,16 @@ int block_current_task(void)
 			task_table[id].prev->next = task_table[id].next;
 		if (task_table[id].next)
 			task_table[id].next->prev = task_table[id].prev;
-		if (runqueues[core_id].queue[prio].first == task_table+id)
-			runqueues[core_id].queue[prio].first = task_table[id].next;
-		if (runqueues[core_id].queue[prio].last == task_table+id) {
-			runqueues[core_id].queue[prio].last = task_table[id].prev;
-			if (!runqueues[core_id].queue[prio].last)
-				runqueues[core_id].queue[prio].last = runqueues[core_id].queue[prio].first;
+		if (runqueues[core_id].queue[prio-1].first == task_table+id)
+			runqueues[core_id].queue[prio-1].first = task_table[id].next;
+		if (runqueues[core_id].queue[prio-1].last == task_table+id) {
+			runqueues[core_id].queue[prio-1].last = task_table[id].prev;
+			if (!runqueues[core_id].queue[prio-1].last)
+				runqueues[core_id].queue[prio-1].last = runqueues[core_id].queue[prio-1].first;
 		}
 
 		// No valid task in queue => update prio_bitmap
-		if (!runqueues[core_id].queue[prio].first)
+		if (!runqueues[core_id].queue[prio-1].first)
 			runqueues[core_id].prio_bitmap &= ~(1 << prio);
 
 		spinlock_unlock(&runqueues[core_id].lock);
@@ -959,16 +966,16 @@ int set_timer(uint64_t deadline)
 			curr_task->prev->next = curr_task->next;
 		if (curr_task->next)
 			curr_task->next->prev = curr_task->prev;
-		if (runqueues[core_id].queue[prio].first == curr_task)
-			runqueues[core_id].queue[prio].first = curr_task->next;
-		if (runqueues[core_id].queue[prio].last == curr_task) {
-			runqueues[core_id].queue[prio].last = curr_task->prev;
-			if (!runqueues[core_id].queue[prio].last)
-				runqueues[core_id].queue[prio].last = runqueues[core_id].queue[prio].first;
+		if (runqueues[core_id].queue[prio-1].first == curr_task)
+			runqueues[core_id].queue[prio-1].first = curr_task->next;
+		if (runqueues[core_id].queue[prio-1].last == curr_task) {
+			runqueues[core_id].queue[prio-1].last = curr_task->prev;
+			if (!runqueues[core_id].queue[prio-1].last)
+				runqueues[core_id].queue[prio-1].last = runqueues[core_id].queue[prio-1].first;
 		}
 
 		// No valid task in queue => update prio_bitmap
-		if (!runqueues[core_id].queue[prio].first)
+		if (!runqueues[core_id].queue[prio-1].first)
 			runqueues[core_id].prio_bitmap &= ~(1 << prio);
 
 		// add task to the timer queue
@@ -1046,15 +1053,15 @@ void scheduler(void)
 			prio = task->prio;
 
 			// add task to the runqueue
-			if (!runqueues[core_id].queue[prio].first) {
-				runqueues[core_id].queue[prio].last = runqueues[core_id].queue[prio].first = task;
+			if (!runqueues[core_id].queue[prio-1].first) {
+				runqueues[core_id].queue[prio-1].last = runqueues[core_id].queue[prio-1].first = task;
 				task->next = task->prev = NULL;
 				runqueues[core_id].prio_bitmap |= (1 << prio);
 			} else {
-				task->prev = runqueues[core_id].queue[prio].last;
+				task->prev = runqueues[core_id].queue[prio-1].last;
 				task->next = NULL;
-				runqueues[core_id].queue[prio].last->next = task;
-				runqueues[core_id].queue[prio].last = task;
+				runqueues[core_id].queue[prio-1].last->next = task;
+				runqueues[core_id].queue[prio-1].last = task;
 			}
 		}
 	}
@@ -1076,13 +1083,13 @@ void scheduler(void)
 			runqueues[core_id].old_task = curr_task;
 		}
 
-		curr_task = per_core(current_task) = runqueues[core_id].queue[prio].first;
+		curr_task = per_core(current_task) = runqueues[core_id].queue[prio-1].first;
 		curr_task->status = TASK_RUNNING;
 
 		// remove new task from queue
-		runqueues[core_id].queue[prio].first = curr_task->next;
+		runqueues[core_id].queue[prio-1].first = curr_task->next;
 		if (!curr_task->next) {
-			runqueues[core_id].queue[prio].last = NULL;
+			runqueues[core_id].queue[prio-1].last = NULL;
 			runqueues[core_id].prio_bitmap &= ~(1 << prio);
 		}
 	}