diff --git a/sched/clock/clock_adjtime.c b/sched/clock/clock_adjtime.c
index 3244ad59d6..f55767fb5a 100644
--- a/sched/clock/clock_adjtime.c
+++ b/sched/clock/clock_adjtime.c
@@ -49,6 +49,7 @@
 
 static struct wdog_s g_adjtime_wdog;
 static long g_adjtime_ppb;
+static spinlock_t g_adjtime_lock = SP_UNLOCKED;
 
 /****************************************************************************
  * Private Functions
@@ -58,8 +59,12 @@ static long g_adjtime_ppb;
 
 static void adjtime_wdog_callback(wdparm_t arg)
 {
+  irqstate_t flags;
+
   UNUSED(arg);
 
+  flags = spin_lock_irqsave(&g_adjtime_lock);
+
 #ifdef CONFIG_ARCH_HAVE_ADJTIME
   up_adjtime(0);
 #endif
@@ -69,6 +74,7 @@ static void adjtime_wdog_callback(wdparm_t arg)
 #endif
 
   g_adjtime_ppb = 0;
+  spin_unlock_irqrestore(&g_adjtime_lock, flags);
 }
 
 /* Query remaining adjustment in microseconds */
@@ -108,7 +114,8 @@ static int adjtime_start(long long adjust_usec)
       ppb = -ppb_limit;
     }
 
-  flags = enter_critical_section();
+  flags = spin_lock_irqsave(&g_adjtime_lock);
+  sched_lock();
 
   /* Set new adjustment */
 
@@ -134,7 +141,8 @@ static int adjtime_start(long long adjust_usec)
       wd_cancel(&g_adjtime_wdog);
     }
 
-  leave_critical_section(flags);
+  spin_unlock_irqrestore(&g_adjtime_lock, flags);
+  sched_unlock();
 
   return ret;
 }