diff --git a/kitty/layout/tall.py b/kitty/layout/tall.py
index 63121c6c9..d86a7f466 100644
--- a/kitty/layout/tall.py
+++ b/kitty/layout/tall.py
@@ -171,7 +171,7 @@ class Tall(Layout):
                 if is_fat:
                     xl, yl = yl, xl
                 yield wg, xl, yl, True
-            size = (lgd.central.bottom if is_fat else lgd.central.right) - start
+            size = 1 + (lgd.central.bottom if is_fat else lgd.central.right) - start
 
         ylayout = self.variable_layout(all_windows, self.biased_map)
         for i, wg in enumerate(all_windows.iter_all_layoutable_groups()):