diff --git a/sysdep/unix/io-loop.h b/sysdep/unix/io-loop.h
index 33d529da..e23a9be0 100644
--- a/sysdep/unix/io-loop.h
+++ b/sysdep/unix/io-loop.h
@@ -9,6 +9,8 @@
 
 #include "lib/rcu.h"
 
+#include <pthread.h>
+
 struct pipe
 {
   int fd[2];