diff --git a/apis/python/src/tiledbsoma/_dataframe.py b/apis/python/src/tiledbsoma/_dataframe.py
index bc07146184..e68a29a8de 100644
--- a/apis/python/src/tiledbsoma/_dataframe.py
+++ b/apis/python/src/tiledbsoma/_dataframe.py
@@ -298,8 +298,7 @@ def create(
             )
 
             if index_column_name == "soma_joinid":
-                lower = slot_core_current_domain[0]
-                upper = slot_core_current_domain[1]
+                (lower, upper) = slot_core_current_domain
                 if lower != 0:
                     raise ValueError(
                         f"domain for soma_joinid must have lower bound of 0; got {lower}"