diff --git a/flox/aggregations.py b/flox/aggregations.py
index 0c2e82bb..f33a0d51 100644
--- a/flox/aggregations.py
+++ b/flox/aggregations.py
@@ -830,7 +830,17 @@ def _initialize_aggregation(
     )
 
     final_dtype = _normalize_dtype(dtype_ or agg.dtype_init["final"], array_dtype, fill_value)
-    if agg.name not in ["first", "last", "nanfirst", "nanlast", "min", "max", "nanmin", "nanmax", "topk"]:
+    if agg.name not in [
+        "first",
+        "last",
+        "nanfirst",
+        "nanlast",
+        "min",
+        "max",
+        "nanmin",
+        "nanmax",
+        "topk",
+    ]:
         final_dtype = _maybe_promote_int(final_dtype)
     agg.dtype = {
         "user": dtype,  # Save to automatically choose an engine