diff --git a/mysql_ch_replicator/converter.py b/mysql_ch_replicator/converter.py
index 48d710e..967e9be 100644
--- a/mysql_ch_replicator/converter.py
+++ b/mysql_ch_replicator/converter.py
@@ -582,13 +582,13 @@ def convert_alter_query(self, mysql_query, db_name):
                 tokens = tokens[1:]
 
             if op_name == 'add':
-                if tokens[0].lower() in ('constraint', 'index', 'foreign', 'unique'):
+                if tokens[0].lower() in ('constraint', 'index', 'foreign', 'unique', 'key'):
                     continue
                 self.__convert_alter_table_add_column(db_name, table_name, tokens)
                 continue
 
             if op_name == 'drop':
-                if tokens[0].lower() in ('constraint', 'index', 'foreign', 'unique'):
+                if tokens[0].lower() in ('constraint', 'index', 'foreign', 'unique', 'key'):
                     continue
                 self.__convert_alter_table_drop_column(db_name, table_name, tokens)
                 continue
diff --git a/test_mysql_ch_replicator.py b/test_mysql_ch_replicator.py
index deac3f1..30759eb 100644
--- a/test_mysql_ch_replicator.py
+++ b/test_mysql_ch_replicator.py
@@ -1420,6 +1420,17 @@ def test_add_column_first_after_and_drop_column(monkeypatch):
     assert_wait(lambda: ch.select(TEST_TABLE_NAME, where="id=44")[0]['c1'] == 111)
     assert_wait(lambda: ch.select(TEST_TABLE_NAME, where="id=44")[0]['c2'] == 222)
 
+    # Test add KEY
+    mysql.execute(
+        f"ALTER TABLE `{TEST_TABLE_NAME}` ADD KEY `idx_c1_c2` (`c1`,`c2`)")
+    mysql.execute(
+        f"INSERT INTO `{TEST_TABLE_NAME}` (id, c1, c2) VALUES (46, 333, 444)",
+        commit=True,
+    )
+    assert_wait(lambda: len(ch.select(TEST_TABLE_NAME, where="id=46")) == 1)
+    assert_wait(lambda: ch.select(TEST_TABLE_NAME, where="id=46")[0]['c1'] == 333)
+    assert_wait(lambda: ch.select(TEST_TABLE_NAME, where="id=46")[0]['c2'] == 444)
+    
     # Test drop column
     mysql.execute(
         f"ALTER TABLE `{TEST_TABLE_NAME}` DROP COLUMN c2")