diff --git a/libc/include/sys/un.h b/libc/include/sys/un.h
index 03ef5e4..83c1d17 100644
--- a/libc/include/sys/un.h
+++ b/libc/include/sys/un.h
@@ -26,8 +26,12 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _SYS_UN_H_
-#define _SYS_UN_H_
+#pragma once
+
+/**
+ * @file sys/un.h
+ * @brief Unix domain sockets.
+ */
 
 #include <bits/sa_family_t.h>
 #include <linux/un.h>
@@ -35,7 +39,6 @@
 
 #if defined(__USE_BSD) || defined(__USE_GNU)
 #include <string.h>
+/** Returns the actual length of the given `sockaddr_un`. */
 #define SUN_LEN(__ptr) (offsetof(struct sockaddr_un, sun_path) + strlen((__ptr)->sun_path))
 #endif
-
-#endif