diff --git a/python/arcticdb/version_store/processing.py b/python/arcticdb/version_store/processing.py
index c23c15f260..336896065d 100644
--- a/python/arcticdb/version_store/processing.py
+++ b/python/arcticdb/version_store/processing.py
@@ -503,16 +503,16 @@ def agg(self, aggregations: Dict[str, Union[str, tuple[str, str]]]):
             len(self.clauses) and isinstance(self.clauses[-1], _GroupByClause),
             f"Aggregation only makes sense after groupby",
         )
-        for v in aggregations.values():
+        for k, v in aggregations.items():
             check(isinstance(v, (str, tuple)), f"Values in agg dict expected to be strings or tuples, received {v} of type {type(v)}")
             if isinstance(v, str):
-                v = v.lower()
+                aggregations[k] = v.lower()
             elif isinstance(v, tuple):
                 check(
                     len(v) == 2 and (isinstance(v[0], str) and isinstance(v[1], str)),
                     f"Tuple values in agg dict expected to have 2 string elements, received {v}"
                 )
-                v[1].lower()
+                aggregations[k] = (v[0], v[1].lower())
 
         self.clauses.append(_AggregationClause(self.clauses[-1].grouping_column, aggregations))
         self._python_clauses.append(PythonAggregationClause(aggregations))
diff --git a/python/tests/unit/arcticdb/version_store/test_aggregation.py b/python/tests/unit/arcticdb/version_store/test_aggregation.py
index d4accb00f0..960bc11a15 100644
--- a/python/tests/unit/arcticdb/version_store/test_aggregation.py
+++ b/python/tests/unit/arcticdb/version_store/test_aggregation.py
@@ -474,8 +474,8 @@ def test_named_agg(lmdb_version_store_tiny_segment):
     q = q.groupby("grouping_column").agg(
         {
             "agg_column_sum": ("agg_column", "sum"),
-            "agg_column_mean": ("agg_column", "mean"),
-            "agg_column": "min",
+            "agg_column_mean": ("agg_column", "MEAN"),
+            "agg_column": "MIN",
         }
     )
     print(f"{q}")