diff --git a/debugger/callstackdlg.pp b/debugger/callstackdlg.pp
index d2cd7cd9c6..a5074cfcfb 100644
--- a/debugger/callstackdlg.pp
+++ b/debugger/callstackdlg.pp
@@ -300,6 +300,9 @@ begin
     MaxCnt := FViewStart + FViewLimit + 1;
     if CStack <> nil then CStack.CountLimited(MaxCnt); // trigger the update-notification, if executed immediately
     FInUpdateView := False;
+    // TODO: must make CStack ref-counted
+    if CStack <> GetSelectedCallstack then exit; // Something changed, maybe debugger stopped
+
 
     if (CStack = nil) or ((Snap <> nil) and (CStack.CountLimited(MaxCnt) = 0)) then begin
       lvCallStack.Items.Clear;
@@ -346,6 +349,8 @@ begin
 
     FInUpdateView := True;
     CStack.PrepareRange(First, Count);
+    // TODO: must make CStack ref-counted
+    if CStack <> GetSelectedCallstack then exit; // Something changed, maybe debugger stopped
     FInUpdateView := False;
     for n := 0 to Count - 1 do
     begin
diff --git a/debugger/debugger.pp b/debugger/debugger.pp
index b712f977e0..da7fc17e3b 100644
--- a/debugger/debugger.pp
+++ b/debugger/debugger.pp
@@ -5354,7 +5354,7 @@ begin
 
   FPreparing := True;
   while ACount > 0 do begin
-    Entries[AIndex];
+    Entries[AIndex]; // Request unknown entries: will set LowesUnknown / HighesUnknown
     inc(AIndex);
     dec(ACount);
   end;