diff --git a/sqlite_utils/db.py b/sqlite_utils/db.py
index 17d79de..b6315dd 100644
--- a/sqlite_utils/db.py
+++ b/sqlite_utils/db.py
@@ -1904,12 +1904,10 @@ class Table(Queryable):
                 if hash_id:
                     all_columns.insert(0, hash_id)
             else:
-                all_columns += [
-                    column
-                    for record in chunk
-                    for column in record
-                    if column not in all_columns
-                ]
+                for record in chunk:
+                    all_columns += [
+                        column for column in record if column not in all_columns
+                    ]
 
             validate_column_names(all_columns)
             first = False
diff --git a/tests/test_create.py b/tests/test_create.py
index bee47a7..2975dea 100644
--- a/tests/test_create.py
+++ b/tests/test_create.py
@@ -569,6 +569,22 @@ def test_insert_replace_rows_alter_table(fresh_db, use_table_factory):
     ] == list(table.rows)
 
 
+def test_insert_all_with_extra_columns_in_later_chunks(fresh_db):
+    chunk = [
+        {"record": "Record 1"},
+        {"record": "Record 2"},
+        {"record": "Record 3"},
+        {"record": "Record 4", "extra": 1},
+    ]
+    fresh_db["t"].insert_all(chunk, batch_size=2, alter=True)
+    assert list(fresh_db["t"].rows) == [
+        {"record": "Record 1", "extra": None},
+        {"record": "Record 2", "extra": None},
+        {"record": "Record 3", "extra": None},
+        {"record": "Record 4", "extra": 1},
+    ]
+
+
 def test_bulk_insert_more_than_999_values(fresh_db):
     "Inserting 100 items with 11 columns should work"
     fresh_db["big"].insert_all(