diff --git a/libc/include/spawn.h b/libc/include/spawn.h
index 3ce402f..f366239 100644
--- a/libc/include/spawn.h
+++ b/libc/include/spawn.h
@@ -46,14 +46,17 @@
 #define POSIX_SPAWN_USEVFORK 64
 #define POSIX_SPAWN_SETSID 128
 #endif
-// mark all fds (except stdin/out/err) as close-on-exec prior to executing registered file actions
+/**
+ * Used with posix_spawnattr_setflags() to mark all fds except
+ * stdin/stdout/stderr as O_CLOEXEC prior to executing registered file actions.
+ */
 #define POSIX_SPAWN_CLOEXEC_DEFAULT 256
 
 typedef struct __posix_spawnattr* posix_spawnattr_t;
 typedef struct __posix_spawn_file_actions* posix_spawn_file_actions_t;
 
-int posix_spawn(pid_t* _Nullable __pid, const char* _Nonnull __path, const posix_spawn_file_actions_t _Nullable * _Nullable __actions, const posix_spawnattr_t _Nullable * _Nullable __attr, char* const _Nonnull __argv[_Nonnull], char* const _Nullable __env[_Nullable]) __INTRODUCED_IN(28);
-int posix_spawnp(pid_t* _Nullable __pid, const char* _Nonnull __file, const posix_spawn_file_actions_t _Nullable * _Nullable __actions, const posix_spawnattr_t _Nullable * _Nullable __attr, char* const _Nonnull __argv[_Nonnull], char* const _Nullable __env[_Nullable]) __INTRODUCED_IN(28);
+int posix_spawn(pid_t* _Nullable __pid, const char* _Nonnull __path, const posix_spawn_file_actions_t _Nullable * _Nullable __actions, const posix_spawnattr_t _Nullable * _Nullable __attr, char* const _Nullable __argv[_Nullable], char* const _Nullable __env[_Nullable]) __INTRODUCED_IN(28);
+int posix_spawnp(pid_t* _Nullable __pid, const char* _Nonnull __file, const posix_spawn_file_actions_t _Nullable * _Nullable __actions, const posix_spawnattr_t _Nullable * _Nullable __attr, char* const _Nullable __argv[_Nullable], char* const _Nullable __env[_Nullable]) __INTRODUCED_IN(28);
 
 int posix_spawnattr_init(posix_spawnattr_t _Nullable * _Nonnull __attr) __INTRODUCED_IN(28);
 int posix_spawnattr_destroy(posix_spawnattr_t _Nonnull * _Nonnull __attr) __INTRODUCED_IN(28);