diff --git a/ChangeLog b/ChangeLog
index af86d2d..89717f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2017-11-16  NIIBE Yutaka  <gniibe@fsij.org>
 
+	* chopstx.h (chopstx_poll): API change.
+	* chopstx.c (chopstx_poll): Use const pointer.
+
 	* chopstx-cortex-m.c (idle): Support WFE.
 	* mcu/usb-stm32f103.c (usb_lld_init): Use event.
 	* usb_lld.h (INTR_REQ_USB_WAKEUP): Remove.
diff --git a/NEWS b/NEWS
index 5e102fc..b77df79 100644
--- a/NEWS
+++ b/NEWS
@@ -16,6 +16,12 @@ sleep by this feature requires careful preparation.  Enabling sleep, a
 board with no RESET pin cannot be debugged by JTAG/SWD.  Setting of
 DBGMCU_CR (0xE0042004) is required beforehand (default is zero).
 
+** API change: chopstx_poll
+This is a kind of clarification.  The third argument is now an array
+of constant pointers.  We don't touch the array itself, just use it.
+This allows having the array in read-only memory and can contribute
+less use of RAM.
+
 ** USB API changes
 INTR_REQ_USB is now defined by usb_lld.h.  Enumeration type of
 DEVICE_STATE now has USB_DEVICE_STATE_ prefix.
diff --git a/chopstx-gnu-linux.c b/chopstx-gnu-linux.c
index 32329ca..9392292 100644
--- a/chopstx-gnu-linux.c
+++ b/chopstx-gnu-linux.c
@@ -346,4 +346,5 @@ chopstx_create_arch (uintptr_t stack_addr, size_t stack_size,
 void
 chx_sleep_mode (int enable_sleep)
 {
+  (void)enable_sleep;
 }
diff --git a/chopstx.c b/chopstx.c
index 31a0d0c..93aaf41 100644
--- a/chopstx.c
+++ b/chopstx.c
@@ -1322,7 +1322,7 @@ chx_proxy_init (struct chx_px *px, uint32_t *cp)
  * Returns number of active descriptors.
  */
 int
-chopstx_poll (uint32_t *usec_p, int n, struct chx_poll_head *pd_array[])
+chopstx_poll (uint32_t *usec_p, int n, struct chx_poll_head *const pd_array[])
 {
   uint32_t counter = 0;
   int i;
diff --git a/chopstx.h b/chopstx.h
index 5c7bd88..64e9557 100644
--- a/chopstx.h
+++ b/chopstx.h
@@ -158,7 +158,8 @@ void chopstx_claim_irq (chopstx_intr_t *intr, uint8_t irq_num);
 void chopstx_intr_wait (chopstx_intr_t *intr); /* DEPRECATED */
 
 
-int chopstx_poll (uint32_t *usec_p, int n, struct chx_poll_head *pd_array[]);
+int chopstx_poll (uint32_t *usec_p, int n,
+		  struct chx_poll_head *const pd_array[]);
 
 int chopstx_conf_idle (int enable_sleep);