Well, basically it is enough to add #yourself in to the class method:

signalLock: aSemaphore afterMSecs: anInteger inMonitor: aMonitor queue: anOrderedCollection
anInteger < 0 ifTrue: [self error: 'delay times cannot be negative'].
^ (self new setDelay: anInteger forSemaphore: aSemaphore monitor: aMonitor queue: anOrderedCollection) schedule; yourself

But I am wondering if it is the only one affected method. 
If someone agree with this solution, I can create test case and slice.

Cheers,
Juraj

24. 2. 2015 v 16:36, Juraj Kubelka <juraj.kubelka@gmail.com>:

Hi!

I have a problem in the recent Pharo 4 image: the method MonitorDelay>>#signalLock:afterMSecs:inMonitor:queue: returns a boolean instead of MonitorDelay object.
And in the method Monitor>>#exitAndWaitInQueue:maxMilliseconds: it raises message not understood on #unschedule.

Pharo #40505.

-=-=-
| monitor |
monitor := Monitor new.
monitor critical: [ monitor waitWhile: [ true ] maxMilliseconds: 200 ].
-=-=-

Is it known error? Someone is changing Monitor or related code?
Thanks,
Juraj