diff --git a/pw_poller.py b/pw_poller.py
index 2e403c0..20a5a08 100755
--- a/pw_poller.py
+++ b/pw_poller.py
@@ -172,6 +172,9 @@ def _process_series(self, pw_series) -> None:
 
         if hasattr(s, 'tree_name') and s.tree_name:
             s.tree_selection_comment = comment
+            if not s.tree_name in self._work_queues:
+                log(f"skip {pw_series['id']} for unknown tree {s.tree_name}", "")
+                return
             self._work_queues[s.tree_name].put(s)
         else:
             core.write_tree_selection_result(self.result_dir, s, comment)