--- libev/ev.c	2007/11/04 18:29:44	1.60
+++ libev/ev.c	2007/11/04 19:45:09	1.61
@@ -796,6 +796,8 @@
     {
       struct ev_timer *w = timers [0];
 
+      assert (("inactive timer on timer heap detected", ev_is_active (w)));
+
       /* first reschedule or stop timer */
       if (w->repeat)
         {
@@ -817,6 +819,8 @@
     {
       struct ev_periodic *w = periodics [0];
 
+      assert (("inactive timer on periodic heap detected", ev_is_active (w)));
+
       /* first reschedule or stop timer */
       if (w->interval)
         {