diff --git a/extra/coredumper/src/thread_lister.c b/extra/coredumper/src/thread_lister.c
index 15fedac..181889b 100644
--- a/extra/coredumper/src/thread_lister.c
+++ b/extra/coredumper/src/thread_lister.c
@@ -35,6 +35,7 @@

 #include <stdio.h> /* needed for NULL on some powerpc platforms (?!) */
 #include <sys/prctl.h>
+#include <unistd.h>

 #include "linuxthreads.h"
 /* Include other thread listers here that define THREADS macro