diff --git a/libc/include/sys/file.h b/libc/include/sys/file.h
index a420021..ccdfeea 100644
--- a/libc/include/sys/file.h
+++ b/libc/include/sys/file.h
@@ -26,8 +26,12 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _SYS_FILE_H_
-#define _SYS_FILE_H_
+#pragma once
+
+/**
+ * @file sys/file.h
+ * @brief The flock() function.
+ */
 
 #include <sys/cdefs.h>
 #include <sys/types.h>
@@ -36,8 +40,12 @@
 
 __BEGIN_DECLS
 
+/**
+ * [flock(2)](http://man7.org/linux/man-pages/man2/flock.2.html) performs
+ * advisory file lock operations.
+ *
+ * Returns 0 on success, and returns -1 and sets `errno` on failure.
+ */
 int flock(int __fd, int __op);
 
 __END_DECLS
-
-#endif