diff --git a/lib/thread.h b/lib/thread.h
index 9743a22..4856dec 100644
--- a/lib/thread.h
+++ b/lib/thread.h
@@ -211,6 +211,7 @@
 extern void thread_call (struct thread *);
 extern unsigned long thread_timer_remain_second (struct thread *);
 extern int thread_should_yield (struct thread *);
+extern unsigned long timeval_elapsed (struct timeval a, struct timeval b);
 
 /* Internal libzebra exports */
 extern void thread_getrusage (RUSAGE_T *);