diff --git a/ide/sourceeditor.pp b/ide/sourceeditor.pp
index 5e5491548a..33b64f6b5d 100644
--- a/ide/sourceeditor.pp
+++ b/ide/sourceeditor.pp
@@ -3494,7 +3494,8 @@ end;
 procedure TSourceEditor.Activate;
 begin
   if (FSourceNoteBook=nil) then exit;
-  FSourceNoteBook.SetActiveSE(Self);
+  if FSourceNoteBook.FUpdateLock = 0 then
+    FSourceNoteBook.SetActiveSE(Self);
 end;
 
 function TSourceEditor.PageIndex: integer;