diff --git a/doc/obsolete-stuff b/doc/obsolete-stuff
index 579ecba4..8d88bd14 100644
--- a/doc/obsolete-stuff
+++ b/doc/obsolete-stuff
@@ -61,6 +61,23 @@ will need to be removed as well.
 
 Sortix currently implement these functions for compatibility reasons.
 
+F_GETLK, F_SETLK, F_SETLKW
+--------------------------
+
+These fcntl commands implement POSIX advisory file locking. Unfortunately, this
+standard interface is very poorly designed. In particular, if a process closes
+a file descriptor, then all locks the process has for that file is unlocked,
+even though there might not be a lock associated with that file descriptor in
+the first place. This means that if the main program locks /foo/bar and runs
+a library routine that also happen to open /foo/bar, then the advsisory lock set
+up by the main program is silently gone when when the library routine closes the
+file and returns to the main program. Additionally, the locks are attached to
+processes, rather than file descriptors. This complicates using them for threads
+and passing file locks onto child processes.
+
+Use the flock (not to be confused with lockf) call instead as it works at a file
+descriptor level.
+
 ftime
 -----
 
@@ -109,6 +126,16 @@ This function is rather pointless. If we use a character encoding that wasn't
 ascii compatible, then it doesn't make sense. If we use a sane character
 encoding such as UTF-8, then you can simply check if the value is at most 127.
 
+lockf
+-----
+
+This function implements POSIX advisory locks. It suffers from the same basic
+design mistakes that the fnctl advistory lock commands (F_GETLK, F_SETLK,
+F_SETLKW) do and should be avoided for the same reasons (see above).
+
+Use the flock (not to be confused with lockf) call instead as it works at a file
+descriptor level.
+
 PATH_MAX
 --------
 
diff --git a/doc/posix-divergence b/doc/posix-divergence
index fed0886c..a6b89eba 100644
--- a/doc/posix-divergence
+++ b/doc/posix-divergence
@@ -23,6 +23,7 @@ likely take a very long time to phase out and wholly remove.
 
 Mandated by POSIX but not implemented in Sortix
 ----
+* POSIX advisory locks (fcntl, lockf) are not implemented.
 * getpgrp is not implemented.
 * <strings.h> has been merged into <string.h>.
 * Numerous namespace violations (will be fixed or documented here).
diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index 7f91f875..22bcfc3b 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
+    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014.
 
     This file is part of the Sortix C Library.
 
@@ -22,8 +22,6 @@
 
 *******************************************************************************/
 
-/* TODO: POSIX-1.2008 compliance is only partial */
-
 #ifndef INCLUDE_FCNTL_H
 #define INCLUDE_FCNTL_H
 
@@ -31,9 +29,10 @@
 
 #include <sys/__/types.h>
 
+#include <sys/stat.h>
+
 #include <sortix/fcntl.h>
 #include <sortix/seek.h>
-#include <sys/stat.h>
 
 __BEGIN_DECLS
 
@@ -51,12 +50,6 @@ __BEGIN_DECLS
 /* Compatibility with Linux and other systems that have this. */
 #define O_ACCMODE (O_READ | O_WRITE | O_EXEC | O_SEARCH)
 
-/* TODO: F_* missing here */
-
-/* TODO: F_RDLCK, F_UNLCK, F_WRLCK missing here */
-
-/* TODO: AT_SYMLINK_FOLLOW missing here */
-
 /* TODO: POSIX_FADV_* missing here */
 
 #ifndef __pid_t_defined
@@ -64,15 +57,6 @@ __BEGIN_DECLS
 typedef __pid_t pid_t;
 #endif
 
-struct flock
-{
-	short l_type; /* Type of lock; F_RDLCK, F_WRLCK, F_UNLCK. */
-	short l_whence; /* Type of lock; F_RDLCK, F_WRLCK, F_UNLCK. */
-	off_t l_start; /* Relative offset in bytes. */
-	off_t l_len; /* Size; if 0 then until EOF. */
-	pid_t l_pid; /* Process ID of the process holding the lock; returned with F_GETLK. */
-};
-
 int creat(const char* path, mode_t mode);
 int fcntl(int fd, int cmd, ...);
 int open(const char* path, int oflag, ...);
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 1ffc5666..76f3ed2a 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -315,7 +315,6 @@ long gethostid(void);
 
 pid_t getpgrp(void);
 pid_t getsid(pid_t);
-int lockf(int, int, off_t);
 int nice(int);
 int pause(void);
 int setregid(gid_t, gid_t);