diff --git a/tiled/adapters/zarr.py b/tiled/adapters/zarr.py
index f7c5e513a..70cd54758 100644
--- a/tiled/adapters/zarr.py
+++ b/tiled/adapters/zarr.py
@@ -200,15 +200,15 @@ async def append_block(
         -------
 
         """
-        old_shape = self._array.shape
-        new_shape = list(old_shape)
-        new_shape[axis] += list(self._array.shape)[axis]  # Extend along axis
+
+        new_shape = list(self._array.shape)
+        new_shape[axis] += list(data.shape)[axis]  # Extend along axis
 
         # Resize the Zarr array to accommodate new data
-        data.resize(tuple(new_shape))
+        self._array.resize(tuple(new_shape))
 
         # Append the new data to the resized array
-        data[-data.shape[0]:] = data  # Slicing to place data at the end
+        self._array[-data.shape[0]:] = data  # Slicing to place data at the end
 
 if sys.version_info < (3, 9):
     from typing_extensions import Mapping