diff --git a/fslite/tests/generate_big_tests.py b/fslite/tests/generate_big_tests.py
index 68413dd..1ea7a31 100644
--- a/fslite/tests/generate_big_tests.py
+++ b/fslite/tests/generate_big_tests.py
@@ -36,10 +36,11 @@ def generate_large_test_dataset():
             chunk_labels = labels[chunk_start:chunk_end]
 
             # Generate chunk of features
-            chunk_features = {
-                f"feature{i}": np.random.rand(chunk_end - chunk_start)
+            # Generate chunk of features
+            chunk_features = (
+                (f"feature{i}", np.random.rand(chunk_end - chunk_start))
                 for i in range(1, n_features + 1)
-            }
+            )
 
             # Create DataFrame chunk
             chunk_data = {"sample_id": chunk_sample_ids, "label": chunk_labels}