diff --git a/src/sqlalchemy_cratedb/dialect.py b/src/sqlalchemy_cratedb/dialect.py
index aebad9c2..58df98f1 100644
--- a/src/sqlalchemy_cratedb/dialect.py
+++ b/src/sqlalchemy_cratedb/dialect.py
@@ -326,7 +326,7 @@ def result_fun(result):
             (table_name, schema or self.default_schema_name)
         )
         pks = result_fun(pk_result)
-        return {'constrained_columns': pks,
+        return {'constrained_columns': list(pks),
                 'name': 'PRIMARY KEY'}
 
     @reflection.cache
diff --git a/tests/dialect_test.py b/tests/dialect_test.py
index d3b5c364..d2213aca 100644
--- a/tests/dialect_test.py
+++ b/tests/dialect_test.py
@@ -88,7 +88,7 @@ def test_primary_keys_2_3_0(self):
         )
         self.fake_cursor.fetchall = MagicMock(return_value=[["id"], ["id2"], ["id3"]])
 
-        eq_(insp.get_pk_constraint("characters")['constrained_columns'], {"id", "id2", "id3"})
+        eq_(insp.get_pk_constraint("characters")['constrained_columns'], ["id", "id2", "id3"])
         self.fake_cursor.fetchall.assert_called_once_with()
         in_("information_schema.key_column_usage", self.executed_statement)
         in_("table_catalog = ?", self.executed_statement)
@@ -103,7 +103,7 @@ def test_primary_keys_3_0_0(self):
         )
         self.fake_cursor.fetchall = MagicMock(return_value=[["id"], ["id2"], ["id3"]])
 
-        eq_(insp.get_pk_constraint("characters")['constrained_columns'], {"id", "id2", "id3"})
+        eq_(insp.get_pk_constraint("characters")['constrained_columns'], ["id", "id2", "id3"])
         self.fake_cursor.fetchall.assert_called_once_with()
         in_("information_schema.key_column_usage", self.executed_statement)
         in_("table_schema = ?", self.executed_statement)