--- a/Tools__BreakpointService.st	Fri Dec 09 12:13:25 2016 +0100
+++ b/Tools__BreakpointService.st	Fri Dec 09 12:14:18 2016 +0100
@@ -415,7 +415,7 @@
     |topView|
 
     (self canCreateOrToggleBreakpointAtLine:nil) ifFalse:[
-        ((topView := codeView topView) class == DebugView) ifTrue:[
+        ((topView := codeView topView) notNil and:[topView isDebugView]) ifTrue:[
             self hasBreakpoints ifFalse:[
                 ^ 'Sorry - cannot add breakpoint in the debugger (would need recompilation)\(can only add breakpoints if stopped at a method breakpoint)' withCRs
             ].