diff --git a/pytools/__init__.py b/pytools/__init__.py
index 80ec93a40933695cbf4ed96ddc040264d09737df..08c3ed1adf549055fb839bb0050c9331c3734668 100644
--- a/pytools/__init__.py
+++ b/pytools/__init__.py
@@ -1784,10 +1784,10 @@ def merge_tables(*tables: Table,
                 entry for i, entry in enumerate(row) if i not in skip_columns
                 ])
 
-    alignments = sum([
+    alignments = sum((
         remove_columns(i, tbl._get_alignments())
         for i, tbl in enumerate(tables)
-        ], ())
+        ), ())
     result = Table(alignments=alignments)
 
     for i in range(tables[0].nrows):