diff --git a/model_tools/activations/core.py b/model_tools/activations/core.py
index ceec93d..543caa5 100644
--- a/model_tools/activations/core.py
+++ b/model_tools/activations/core.py
@@ -126,7 +126,8 @@ def register_stimulus_set_hook(self, hook):
         return handle
 
     def _get_activations_batched(self, paths, layers, batch_size):
-        layer_activations = None
+        from collections import OrderedDict
+        layer_activations = OrderedDict()
         for batch_start in tqdm(range(0, len(paths), batch_size), unit_scale=batch_size, desc="activations"):
             batch_end = min(batch_start + batch_size, len(paths))
             batch_inputs = paths[batch_start:batch_end]
@@ -134,11 +135,11 @@ def _get_activations_batched(self, paths, layers, batch_size):
             for hook in self._batch_activations_hooks.copy().values():  # copy to avoid handle re-enabling messing with the loop
                 batch_activations = hook(batch_activations)
 
-            if layer_activations is None:
-                layer_activations = copy.copy(batch_activations)
-            else:
-                for layer_name, layer_output in batch_activations.items():
-                    layer_activations[layer_name] = np.concatenate((layer_activations[layer_name], layer_output))
+            for layer_name, layer_output in batch_activations.items():
+                layer_activations.setdefault(layer_name, []).append(layer_output)
+
+        for layer_name, layer_outputs in layer_activations.items():
+            layer_activations[layer_name] = np.concatenate(layer_outputs)
 
         return layer_activations