--- a/ProcessorScheduler.st	Thu Nov 03 20:16:07 2016 +0100
+++ b/ProcessorScheduler.st	Thu Nov 03 20:23:47 2016 +0100
@@ -1593,7 +1593,8 @@
         prio := prio - 1
     ].
 
-    (scheduledProcesses contains:[:p | p notNil and:[p isUserProcess] ]) ifTrue:[
+    (scheduledProcesses notNil 
+    and:[scheduledProcesses contains:[:p | p notNil and:[p isUserProcess] ]]) ifTrue:[
         ^ true.
     ].