diff --git a/moo/kernel/Process.moo b/moo/kernel/Process.moo
index fe7e18b..9291265 100644
--- a/moo/kernel/Process.moo
+++ b/moo/kernel/Process.moo
@@ -160,7 +160,11 @@ method(#class,#abstract) xxx. => method(#class) xxx { self subclassResponsibilit
 	{
 		| x |
 		x := self _wait.
-		if (x signalAction notNil) { x signalAction value: x }.
+		if (x notError)
+		{
+			## TODO: is it better to check if x is an instance of Semaphore/SemaphoreGroup?
+			if (x signalAction notNil) { x signalAction value: x }.
+		}.
 		^x
 	}
 
diff --git a/moo/kernel/Socket.moo b/moo/kernel/Socket.moo
index 1c602a8..ee64ffc 100644
--- a/moo/kernel/Socket.moo
+++ b/moo/kernel/Socket.moo
@@ -612,7 +612,7 @@ error -> exception
 		].
 
 		[
-			| s s2 st |
+			| s s2 st sg |
 			[
 				s := Socket domain: Socket.Domain.INET type: Socket.Type.STREAM.
 				##s connect: (SocketAddress fromString: '127.0.0.1:9999') do: conact.
@@ -624,13 +624,25 @@ error -> exception
 ##				###s2 listen: 10; watchInput.
 ##				s2 listen: 10 do: accact.
 
+st := Semaphore new.
+System addAsyncSemaphore: st.
+System signal: st afterSecs: 5.
+'JJJJJJJJJJJ' dump.
+sg := SemaphoreGroup new.
+'JJJJJJJJJJJ' dump.
+sg wait.
+'YYYYYYYYYYYYYYY' dump.
+
 ###[ while (1) { '1111' dump. System sleepForSecs: 1 } ] fork.
 
+st := Semaphore new.
+System addAsyncSemaphore: st.
+System signal: st afterSecs: 20.
+
 				while (true)
 				{
 					if (System handleAsyncEvent isError) { break }.
 				}.
-				
 			]
 			ensure:
 			[
diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index 2230101..cb32588 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -937,11 +937,11 @@ static MOO_INLINE moo_oop_t await_semaphore_group (moo_t* moo, moo_oop_semaphore
 		return (moo_oop_t)sem;
 	}
 
-/*MOO_DEBUG1 (moo, "QQQQQQQQQQQQQQQQQQQQQQQ %d\n", semgrp->sem_io_count);
+MOO_DEBUG1 (moo, "QQQQQQQQQQQQQQQQQQQQQQQ %d\n", semgrp->sem_io_count);
 if (MOO_OOP_TO_SMOOI(semgrp->sem_io_count) <= 0)
 {
-	return MOO_ERROR_TO_OOP(MOO_EIOERR);
-}*/
+	//return MOO_ERROR_TO_OOP(MOO_EIOERR);
+}
 
 	/* no semaphores have been signaled. suspend the current process
 	 * until at least one of them is signaled */
@@ -4034,7 +4034,7 @@ static MOO_INLINE int switch_process_if_needed (moo_t* moo)
 				/* [NOTE] no moo_pushtmp() on proc. no GC must occur
 				 *        in the following line until it's used for
 				 *        wake_process() below. */
-				delete_from_sem_heap (moo, 0); /* moo->sem_heap_count is decremented */
+				delete_from_sem_heap (moo, 0); /* moo->sem_heap_count is decremented in delete_from_sem_heap() */
 
 				/* if no process is waiting on the semaphore, 
 				 * signal_semaphore() returns moo->_nil. */