diff --git a/LibC/fcntl.h b/LibC/fcntl.h
index b49d3ef372..78aac1abdf 100644
--- a/LibC/fcntl.h
+++ b/LibC/fcntl.h
@@ -55,6 +55,7 @@ __BEGIN_DECLS
 
 int fcntl(int fd, int cmd, ...);
 
+#define F_RDLCK 0
 #define F_WRLCK 1
 #define F_UNLCK 2