diff --git a/CHANGES b/CHANGES
index 4835cde532..4bab20c1d8 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,8 @@
+2254.	[bug]		timer.c:dispatch() failed to lock timer->lock
+			when reading timer->idle allowing it to see
+			intermediate values as timer->idle was reset by
+			isc_timer_touch(). [RT #17243]
+
 	--- 9.5.0a7 released ---
 
 2253.	[func]	 	"max-cache-size" defaults to 32M.
diff --git a/lib/isc/timer.c b/lib/isc/timer.c
index ccad8f6692..fb599796d8 100644
--- a/lib/isc/timer.c
+++ b/lib/isc/timer.c
@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: timer.c,v 1.80 2007/06/19 23:47:17 tbox Exp $ */
+/* $Id: timer.c,v 1.81 2007/10/24 00:57:23 marka Exp $ */
 
 /*! \file */
 
@@ -581,6 +581,7 @@ dispatch(isc_timermgr_t *manager, isc_time_t *now) {
 	isc_eventtype_t type = 0;
 	isc_timer_t *timer;
 	isc_result_t result;
+	isc_boolean_t idle;
 
 	/*!
 	 * The caller must be holding the manager lock.
@@ -612,23 +613,33 @@ dispatch(isc_timermgr_t *manager, isc_time_t *now) {
 				type = ISC_TIMEREVENT_LIFE;
 				post_event = ISC_TRUE;
 				need_schedule = ISC_FALSE;
-			} else if (!isc_time_isepoch(&timer->idle) &&
-				   isc_time_compare(now,
-						    &timer->idle) >= 0) {
-				type = ISC_TIMEREVENT_IDLE;
-				post_event = ISC_TRUE;
-				need_schedule = ISC_FALSE;
 			} else {
-				/*
-				 * Idle timer has been touched; reschedule.
-				 */
-				XTRACEID(isc_msgcat_get(isc_msgcat,
-							ISC_MSGSET_TIMER,
-							ISC_MSG_IDLERESCHED,
-							"idle reschedule"),
-					 timer);
-				post_event = ISC_FALSE;
-				need_schedule = ISC_TRUE;
+				idle = ISC_FALSE;
+
+				LOCK(&timer->lock);
+				if (!isc_time_isepoch(&timer->idle) &&
+				    isc_time_compare(now,
+						     &timer->idle) >= 0) {
+					idle = ISC_TRUE;
+				}
+				UNLOCK(&timer->lock);
+				if (idle) {
+					type = ISC_TIMEREVENT_IDLE;
+					post_event = ISC_TRUE;
+					need_schedule = ISC_FALSE;
+				} else {
+					/*
+					 * Idle timer has been touched;
+					 * reschedule.
+					 */
+					XTRACEID(isc_msgcat_get(isc_msgcat,
+								ISC_MSGSET_TIMER,
+								ISC_MSG_IDLERESCHED,
+								"idle reschedule"),
+						 timer);
+					post_event = ISC_FALSE;
+					need_schedule = ISC_TRUE;
+				}
 			}
 
 			if (post_event) {