diff --git a/ChangeLog b/ChangeLog
index d4d7c1c6..5f268c2c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -101,6 +101,7 @@ Changes in current version:
  o Make vsnprintf() returns consistent on win32.
  o Fix connection keep-alive behavior for HTTP/1.0
  o Fix use of freed memory in event_reinit; pointed out by Peter Postma
+ o constify struct timeval * where possible
 
 Changes in 1.4.0:
  o allow \r or \n individually to separate HTTP headers instead of the standard "\r\n"; from Charles Kerr.
diff --git a/event.c b/event.c
index 20d46a42..47fef92c 100644
--- a/event.c
+++ b/event.c
@@ -124,7 +124,8 @@ int (*event_sigcb)(void);		/* Signal callback when gotsig is set */
 volatile sig_atomic_t event_gotsig;	/* Set in signal handler */
 
 /* Prototypes */
-static inline int event_add_internal(struct event *ev, struct timeval *tv);
+static inline int event_add_internal(struct event *ev,
+    const struct timeval *tv);
 static inline int event_del_internal(struct event *ev);
 static inline void event_active_internal(struct event *ev, int res,short count);
 
@@ -573,14 +574,14 @@ event_loopexit_cb(evutil_socket_t fd, short what, void *arg)
 
 /* not thread safe */
 int
-event_loopexit(struct timeval *tv)
+event_loopexit(const struct timeval *tv)
 {
 	return (event_once(-1, EV_TIMEOUT, event_loopexit_cb,
 		    current_base, tv));
 }
 
 int
-event_base_loopexit(struct event_base *event_base, struct timeval *tv)
+event_base_loopexit(struct event_base *event_base, const struct timeval *tv)
 {
 	return (event_base_once(event_base, -1, EV_TIMEOUT, event_loopexit_cb,
 		    event_base, tv));
@@ -718,7 +719,7 @@ event_once_cb(evutil_socket_t fd, short events, void *arg)
 int
 event_once(evutil_socket_t fd, short events,
     void (*callback)(evutil_socket_t, short, void *),
-	void *arg, struct timeval *tv)
+	void *arg, const struct timeval *tv)
 {
 	return event_base_once(current_base, fd, events, callback, arg, tv);
 }
@@ -727,7 +728,7 @@ event_once(evutil_socket_t fd, short events,
 int
 event_base_once(struct event_base *base, evutil_socket_t fd, short events,
     void (*callback)(evutil_socket_t, short, void *),
-	void *arg, struct timeval *tv)
+	void *arg, const struct timeval *tv)
 {
 	struct event_once *eonce;
 	struct timeval etv;
@@ -825,7 +826,8 @@ event_assign(struct event *ev, struct event_base *base, evutil_socket_t fd, shor
 
 void
 evperiodic_assign(struct event *ev, struct event_base *base,
-    struct timeval *tv, void (*cb)(evutil_socket_t, short, void *), void *arg)
+    const struct timeval *tv,
+    void (*cb)(evutil_socket_t, short, void *), void *arg)
 {
 	event_assign(ev, base, -1, EV_TIMEOUT, cb, arg);
 	
@@ -924,7 +926,7 @@ event_get_fd(struct event *ev)
 }
 
 int
-event_add(struct event *ev, struct timeval *tv)
+event_add(struct event *ev, const struct timeval *tv)
 {
 	int res;
 
@@ -938,7 +940,7 @@ event_add(struct event *ev, struct timeval *tv)
 }
 
 static inline int
-event_add_internal(struct event *ev, struct timeval *tv)
+event_add_internal(struct event *ev, const struct timeval *tv)
 {
 	struct event_base *base = ev->ev_base;
 	const struct eventop *evsel = base->evsel;
diff --git a/include/event2/event.h b/include/event2/event.h
index e837197b..5702b939 100644
--- a/include/event2/event.h
+++ b/include/event2/event.h
@@ -224,7 +224,7 @@ int event_base_loop(struct event_base *, int);
   @return 0 if successful, or -1 if an error occurred
   @see event_loopexit()
  */
-int event_base_loopexit(struct event_base *, struct timeval *);
+int event_base_loopexit(struct event_base *, const struct timeval *);
 
 /**
   Abort the active event_base_loop() immediately.
@@ -255,7 +255,7 @@ int event_base_loopbreak(struct event_base *);
 */
 
 void evperiodic_assign(struct event *ev, struct event_base *base,
-    struct timeval *tv, void (*cb)(int, short, void *), void *arg);
+    const struct timeval *tv, void (*cb)(int, short, void *), void *arg);
 
 /* Flags to pass to event_set(), event_new(), event_assign(),
  * event_pending()... */
@@ -396,7 +396,7 @@ void event_free(struct event *);
   @return 0 if successful, or -1 if an error occurred
   @see event_once()
  */
-int event_base_once(struct event_base *, evutil_socket_t, short, void (*)(evutil_socket_t, short, void *), void *, struct timeval *);
+int event_base_once(struct event_base *, evutil_socket_t, short, void (*)(evutil_socket_t, short, void *), void *, const struct timeval *);
 
 /**
   Add an event to the set of monitored events.
@@ -416,7 +416,7 @@ int event_base_once(struct event_base *, evutil_socket_t, short, void (*)(evutil
   @return 0 if successful, or -1 if an error occurred
   @see event_del(), event_set()
   */
-int event_add(struct event *, struct timeval *);
+int event_add(struct event *, const struct timeval *);
 
 /**
   Remove an event from the set of monitored events.
diff --git a/include/event2/event_compat.h b/include/event2/event_compat.h
index ee789e35..c9a86ccf 100644
--- a/include/event2/event_compat.h
+++ b/include/event2/event_compat.h
@@ -103,7 +103,7 @@ int event_loop(int);
   @return 0 if successful, or -1 if an error occurred
   @see event_loop(), event_base_loop(), event_base_loopexit()
   */
-int event_loopexit(struct timeval *);
+int event_loopexit(const struct timeval *);
 
 
 /**
@@ -138,7 +138,8 @@ int event_loopbreak(void);
   @see event_set()
 
  */
-int event_once(evutil_socket_t , short, void (*)(evutil_socket_t, short, void *), void *, struct timeval *);
+int event_once(evutil_socket_t , short,
+    void (*)(evutil_socket_t, short, void *), void *, const struct timeval *);
 
 
 /**