diff --git a/libc/include/bits/lockf.h b/libc/include/bits/lockf.h
index d814807..a0ba19d 100644
--- a/libc/include/bits/lockf.h
+++ b/libc/include/bits/lockf.h
@@ -30,6 +30,7 @@
 #define _BITS_LOCKF_H_
 
 #include <sys/cdefs.h>
+#include <sys/types.h>
 
 #define F_ULOCK 0
 #define F_LOCK 1