diff --git a/llms/mlx_lm/tuner/datasets.py b/llms/mlx_lm/tuner/datasets.py
index c75171e5..1a86fb9f 100644
--- a/llms/mlx_lm/tuner/datasets.py
+++ b/llms/mlx_lm/tuner/datasets.py
@@ -87,7 +87,8 @@ class CompletionsDatasetCollection:
         self.collection = data
 
     def __getitem__(self, idx: int):
-        item = next(self.collection)
+        iteration = iter(self.collection)
+        item = next(iteration)
 
         curr_idx = idx
 
@@ -97,7 +98,7 @@ class CompletionsDatasetCollection:
                     return item[curr_idx]
                 else:
                     curr_idx -= len(item)
-                    item = next(self.collection)
+                    item = next(iteration)
             except StopIteration:
                 raise IndexError(idx)