diff --git a/src/or/connection.c b/src/or/connection.c
index e0a5b100f7..c6a45eb308 100644
--- a/src/or/connection.c
+++ b/src/or/connection.c
@@ -136,6 +136,22 @@ connection_t *connection_new(int type) {
   return conn;
 }
 
+/** Tell libevent that we don't care about <b>conn</b> any more. */
+void
+connection_unregister(connection_t *conn)
+{
+  if (conn->read_event) {
+    if (event_del(conn->read_event))
+      log_fn(LOG_WARN, "Error removing read event for %d", (int)conn->s);
+    tor_free(conn->read_event);
+  }
+  if (conn->write_event) {
+    if (event_del(conn->write_event))
+      log_fn(LOG_WARN, "Error removing write event for %d", (int)conn->s);
+    tor_free(conn->write_event);
+  }
+}
+
 /** Deallocate memory used by <b>conn</b>. Deallocate its buffers if necessary,
  * close its socket if necessary, and mark the directory as dirty if <b>conn</b>
  * is an OR or OP connection.
@@ -163,14 +179,8 @@ _connection_free(connection_t *conn) {
   tor_free(conn->nickname);
   tor_free(conn->socks_request);
 
-  if (conn->read_event) {
-    event_del(conn->read_event);
-    tor_free(conn->read_event);
-  }
-  if (conn->write_event) {
-    event_del(conn->write_event);
-    tor_free(conn->write_event);
-  }
+  connection_unregister(conn);
+
   if (conn->s >= 0) {
     log_fn(LOG_INFO,"closing fd %d.",conn->s);
     tor_close_socket(conn->s);
@@ -310,14 +320,9 @@ void connection_close_immediate(connection_t *conn)
            conn->s, CONN_TYPE_TO_STRING(conn->type),
            conn->state, (int)conn->outbuf_flushlen);
   }
-  if (conn->read_event) {
-    event_del(conn->read_event);
-    tor_free(conn->read_event);
-  }
-  if (conn->write_event) {
-    event_del(conn->write_event);
-    tor_free(conn->write_event);
-  }
+
+  connection_unregister(conn);
+
   tor_close_socket(conn->s);
   conn->s = -1;
   if (!connection_is_listener(conn)) {
diff --git a/src/or/main.c b/src/or/main.c
index 74b7b7dcda..1460f15b62 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -162,14 +162,7 @@ int connection_remove(connection_t *conn) {
     return 0;
   }
 
-  if (conn->read_event) {
-    event_del(conn->read_event);
-    tor_free(conn->read_event);
-  }
-  if (conn->write_event) {
-    event_del(conn->write_event);
-    tor_free(conn->write_event);
-  }
+  connection_unregister(conn);
 
   /* replace this one with the one at the end */
   nfds--;
@@ -235,34 +228,45 @@ void get_connection_array(connection_t ***array, int *n) {
   *n = nfds;
 }
 
-/** Set the event mask on <b>conn</b> to <b>events</b>.  (The form of
-* the event mask is DOCDOC)
+/** Set the event mask on <b>conn</b> to <b>events</b>.  (The event
+* mask is a bitmask whose bits are EV_READ and EV_WRITE.)
  */
 void connection_watch_events(connection_t *conn, short events) {
+  int r;
+
   tor_assert(conn);
   tor_assert(conn->read_event);
   tor_assert(conn->write_event);
 
   if (events & EV_READ) {
-    event_add(conn->read_event, NULL);
+    r = event_add(conn->read_event, NULL);
   } else {
-    event_del(conn->read_event);
+    r = event_del(conn->read_event);
   }
 
+  if (r<0)
+    log_fn(LOG_WARN,
+           "Error from libevent setting read event state for %d to %swatched.",
+           (int)conn->s, (events & EV_READ)?"":"un");
+
   if (events & EV_WRITE) {
-    event_add(conn->write_event, NULL);
+    r = event_add(conn->write_event, NULL);
   } else {
-    event_del(conn->write_event);
+    r = event_del(conn->write_event);
   }
+
+  if (r<0)
+    log_fn(LOG_WARN,
+           "Error from libevent setting read event state for %d to %swatched.",
+           (int)conn->s, (events & EV_WRITE)?"":"un");
 }
 
 /** Return true iff <b>conn</b> is listening for read events. */
 int connection_is_reading(connection_t *conn) {
+  int r;
   tor_assert(conn);
 
-  /* This isn't 100% documented, but it should work. */
-  return conn->read_event &&
-    (conn->read_event->ev_flags & (EVLIST_INSERTED|EVLIST_ACTIVE));
+  return conn->read_event && event_pending(conn->read_event, EV_READ, NULL);
 }
 
 /** Tell the main loop to stop notifying <b>conn</b> of any read events. */
@@ -271,7 +275,9 @@ void connection_stop_reading(connection_t *conn) {
   tor_assert(conn->read_event);
 
   log(LOG_DEBUG,"connection_stop_reading() called.");
-  event_del(conn->read_event);
+  if (event_del(conn->read_event))
+    log_fn(LOG_WARN, "Error from libevent setting read event state for %d to unwatched.",
+           (int)conn->s);
 }
 
 /** Tell the main loop to start notifying <b>conn</b> of any read events. */
@@ -279,16 +285,16 @@ void connection_start_reading(connection_t *conn) {
   tor_assert(conn);
   tor_assert(conn->read_event);
 
-  event_add(conn->read_event, NULL);
+  if (event_add(conn->read_event, NULL))
+    log_fn(LOG_WARN, "Error from libevent setting read event state for %d to watched.",
+           (int)conn->s);
 }
 
 /** Return true iff <b>conn</b> is listening for write events. */
 int connection_is_writing(connection_t *conn) {
   tor_assert(conn);
 
-  /* This isn't 100% documented, but it should work. */
-  return conn->write_event &&
-    (conn->write_event->ev_flags & (EVLIST_INSERTED|EVLIST_ACTIVE));
+  return conn->write_event && event_pending(conn->write_event, EV_WRITE, NULL);
 }
 
 /** Tell the main loop to stop notifying <b>conn</b> of any write events. */
@@ -296,7 +302,10 @@ void connection_stop_writing(connection_t *conn) {
   tor_assert(conn);
   tor_assert(conn->write_event);
 
-  event_del(conn->write_event);
+  if (event_del(conn->write_event))
+    log_fn(LOG_WARN, "Error from libevent setting write event state for %d to unwatched.",
+           (int)conn->s);
+
 }
 
 /** Tell the main loop to start notifying <b>conn</b> of any write events. */
@@ -304,7 +313,9 @@ void connection_start_writing(connection_t *conn) {
   tor_assert(conn);
   tor_assert(conn->write_event);
 
-  event_add(conn->write_event, NULL);
+  if (event_add(conn->write_event, NULL))
+    log_fn(LOG_WARN, "Error from libevent setting write event state for %d to watched.",
+           (int)conn->s);
 }
 
 /** DOCDOC */
@@ -937,7 +948,9 @@ static void second_elapsed_callback(int fd, short event, void *args)
   }
 #endif
 
-  evtimer_add(timeout_event, &one_second);
+  if (evtimer_add(timeout_event, &one_second))
+    log_fn(LOG_ERR,
+           "Error from libevent when setting one-second timeout event");
 }
 
 /** Called when we get a SIGHUP: reload configuration files and keys,
@@ -1235,7 +1248,9 @@ void handle_signals(int is_parent)
     for (i = 0; signals[i] >= 0; ++i) {
       signal_set(&signal_events[i], signals[i], signal_callback,
                  (void*)(uintptr_t)signals[i]);
-      signal_add(&signal_events[i], NULL);
+      if (signal_add(&signal_events[i], NULL))
+        log_fn(LOG_WARN, "Error from libevent when adding event for signal %d",
+               signals[i]);
     }
   } else {
     struct sigaction action;
diff --git a/src/or/or.h b/src/or/or.h
index bcd8345d03..d864115b84 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -1195,6 +1195,7 @@ extern const char *conn_type_to_string[];
 extern const char *conn_state_to_string[][_CONN_TYPE_MAX+1];
 
 connection_t *connection_new(int type);
+void connection_unregister(connection_t *conn);
 void connection_free(connection_t *conn);
 void connection_free_all(void);
 void connection_about_to_close_connection(connection_t *conn);