diff --git a/Fill.py b/Fill.py
index e89db1bd436c..342c155079dd 100644
--- a/Fill.py
+++ b/Fill.py
@@ -792,6 +792,9 @@ def failed(warning: str, force: typing.Union[bool, str]) -> None:
                 block['force'] = 'silent'
             if 'from_pool' not in block:
                 block['from_pool'] = True
+            elif not isinstance(block['from_pool'], bool):
+                from_pool_type = type(block['from_pool'])
+                raise Exception(f'Plando "from_pool" has to be boolean, not {from_pool_type} for player {player}.')
             if 'world' not in block:
                 target_world = False
             else: