diff --git a/src/doc/manual/extensions/mp_ref_barrier.txi b/src/doc/manual/extensions/mp_ref_barrier.txi
index cc5a6d66e..8cd3d7043 100644
--- a/src/doc/manual/extensions/mp_ref_barrier.txi
+++ b/src/doc/manual/extensions/mp_ref_barrier.txi
@@ -55,8 +55,11 @@ Returns the number of threads waiting on @var{barrier}.
 @lspdef mp:barrier-wait
 
 @defun mp:barrier-wait barrier
-The caller thread waits on @var{barrier}. When the barrier is
-saturated then all threads waiting on it are unblocked.
+The caller thread waits on @var{barrier}. When the barrier is saturated
+then all threads waiting on it are unblocked. Returns @code{t} if the
+calling thread had to wait to pass the barrier, @code{:unblocked} if the
+barrier is enabled but could be passed without waiting and @code{nil} if
+the barrier is disabled.
 @end defun
 
 
@@ -73,5 +76,7 @@ disabled then all calls to @coderef{mp:barrier-wait} immedietely
 return.
 
 @var{kill-waiting} is used to kill all woken threads.
+
+Returns no values.
 @end defun
 
diff --git a/src/doc/manual/extensions/mp_ref_cv.txi b/src/doc/manual/extensions/mp_ref_cv.txi
index 0618e688f..581963c21 100644
--- a/src/doc/manual/extensions/mp_ref_cv.txi
+++ b/src/doc/manual/extensions/mp_ref_cv.txi
@@ -29,8 +29,8 @@ Creates a condition variable.
 Release @var{lock} and suspend thread until
 @coderef{mp:condition-variable-signal} or
 @coderef{mp:condition-variable-broadcast} is called on @var{cv}. When
-thread resumes re-aquire @var{lock}. May signal an error if @var{lock}
-is not owned by the current thread.
+thread resumes re-aquire @var{lock}. Always returns @code{t}. May signal
+an error if @var{lock} is not owned by the current thread.
 
 @strong{Note:} In some circumstances, the thread may wake up even if no
 call to @coderef{mp:condition-variable-signal} or
@@ -54,8 +54,8 @@ behaviour is undefined if this constraint is violated.
 
 @defun mp:condition-variable-timedwait cv lock seconds
 @coderef{mp:condition-variable-wait} which timeouts after @var{seconds}
-seconds. May signal an error if @var{lock} is not owned by the current
-thread.
+seconds. Returns @code{nil} on timeout and @code{t} otherwise. May
+signal an error if @var{lock} is not owned by the current thread.
 @end defun
 
 
@@ -68,6 +68,7 @@ thread.
 @defun mp:condition-variable-signal cv
 Wake up at least one of the waiters of @var{cv}. Usually, this will wake
 up only a single thread, but it may also wake up multiple threads.
+Always returns @code{t}.
 
 See @coderef{mp:condition-variable-wait}.
 @end defun
@@ -80,7 +81,7 @@ See @coderef{mp:condition-variable-wait}.
 @end deftypefun
 
 @defun mp:condition-variable-broadcast cv
-Wake up all waiters of @var{cv}.
+Wake up all waiters of @var{cv}. Always returns @code{t}.
 
 See @coderef{mp:condition-variable-wait}.  
 @end defun
diff --git a/src/doc/manual/extensions/mp_ref_sem.txi b/src/doc/manual/extensions/mp_ref_sem.txi
index 068181698..4d09c1606 100644
--- a/src/doc/manual/extensions/mp_ref_sem.txi
+++ b/src/doc/manual/extensions/mp_ref_sem.txi
@@ -75,7 +75,7 @@ would not be negative.
 Else blocks until the semaphore can be decremented. Returns the old
 count of @var{semaphore} on success.
 
-If timeout is not @code{niL}, it is the maximum number of seconds to
+If timeout is not @code{nil}, it is the maximum number of seconds to
 wait. If the count cannot be decremented in that time, returns
 @code{nil} without decrementing the count.
 @end defun
@@ -119,5 +119,6 @@ This function is equivalent to @code{(mp:semaphore-wait semaphore count 0)}
 @end deftypefun
 
 @defun mp:signal-semaphore semaphore &optional (count 1)
-Releases @var{count} units of a resource on @var{semaphore}.
+Releases @var{count} units of a resource on @var{semaphore}. Returns no
+values.
 @end defun