diff --git a/lib/libkse/thread/thr_mutex.c b/lib/libkse/thread/thr_mutex.c
index a2a7ed5d381..228e650d6cb 100644
--- a/lib/libkse/thread/thr_mutex.c
+++ b/lib/libkse/thread/thr_mutex.c
@@ -36,6 +36,7 @@
 #include <sys/param.h>
 #include <sys/queue.h>
 #include <pthread.h>
+#include <pthread_np.h>
 #include "un-namespace.h"
 #include "thr_private.h"