diff --git a/environments/factory/base_factory.py b/environments/factory/base_factory.py
index 0627aba..a8b4dda 100644
--- a/environments/factory/base_factory.py
+++ b/environments/factory/base_factory.py
@@ -147,12 +147,13 @@ class BaseFactory:
         pos_x, pos_y = positions[0]  # a.flatten()
         return pos_x, pos_y
 
-    def free_cells(self, excluded_slices: Union[None, List, int] = None) -> np.ndarray:
+    def free_cells(self, excluded_slices: Union[None, List[int], int] = None) -> np.ndarray:
         excluded_slices = excluded_slices or []
         assert isinstance(excluded_slices, (int, list))
         excluded_slices = excluded_slices if isinstance(excluded_slices, list) else [excluded_slices]
 
         state = self.state
+
         if excluded_slices:
             # Todo: Is there a cleaner way?
             inds = list(range(self.state.shape[0]))
@@ -160,6 +161,7 @@ class BaseFactory:
             state = self.state[[x for x in inds if x not in excluded_slices]]
 
         free_cells = state.sum(0)
+        free_cells[excluded_slices] = 0
         free_cells = np.argwhere(free_cells == h.IS_FREE_CELL)
         np.random.shuffle(free_cells)
         return free_cells