diff --git a/znh5md/misc.py b/znh5md/misc.py
index fd569b7d..f8e54524 100644
--- a/znh5md/misc.py
+++ b/znh5md/misc.py
@@ -24,21 +24,19 @@ def concatenate_varying_shape_arrays(
     """
 
     # Determine the maximum shape along all dimensions
-    maxshape = list(values[0].shape)
-    for value in values[1:]:
-        maxshape = [max(a, b) for a, b in zip(maxshape, value.shape)]
+    shapes = np.array([value.shape for value in values])
+    maxshape = tuple(np.max(shapes, axis=0))
 
     # Add the batch dimension
     maxshape = (len(values), *maxshape)
 
-    # Create an array filled with the fillvalue
+    # Create the array filled with the fillvalue
     dataset = np.full(maxshape, fillvalue, dtype=dtype)
-
-    # Insert each value into the dataset
+    
+    # Get the slices for each value and assign them all at once
     for i, value in enumerate(values):
-        # Create slices for each dimension of the current value
-        slices = tuple(slice(0, dim) for dim in value.shape)
-        dataset[(i,) + slices] = value
+        slices = (i,) + tuple(slice(0, dim) for dim in value.shape)
+        dataset[slices] = value
 
     return dataset