diff --git a/ChangeLog b/ChangeLog
index 295c2b2..55bc7e1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2016-05-23  NIIBE Yutaka  <gniibe@fsij.org>
 
+	* chopstx.c (chopstx_poll): Fix a race.  Check COUNTER.
+
 	* example-cdc/usb-cdc.c (tty_input_char): Include newline.
 	* example-cdc/sample.c: Handle newline.
 
diff --git a/chopstx.c b/chopstx.c
index a407086..ac0d49b 100644
--- a/chopstx.c
+++ b/chopstx.c
@@ -1801,6 +1801,11 @@ chopstx_poll (uint32_t *usec_p, int n, ...)
 	{
 	  chopstx_testcancel ();
 	  chx_cpu_sched_lock ();
+	  if (counter)
+	    {
+	      chx_cpu_sched_unlock ();
+	      break;
+	    }
 	  r = chx_snooze (THREAD_WAIT_POLL, usec_p);
 	}
       while (r == 0);