SQLite3Adapter#type_cast should not mutate arguments

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -251,7 +251,7 @@ def type_cast(value, column) # :nodoc:
         value = super
         if column.type == :string && value.encoding == Encoding::ASCII_8BIT
           logger.error "Binary data inserted for `string` type on column `#{column.name}`" if logger
-          value.encode! 'utf-8'
+          value = value.encode Encoding::UTF_8
         end
         value
       end

activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb

@@ -154,6 +154,12 @@ def test_quote_binary_column_escapes_it
         DualEncoding.connection.drop_table('dual_encodings')
       end
 
+      def test_type_cast_should_not_mutate_encoding
+        name  = 'hello'.force_encoding(Encoding::ASCII_8BIT)
+        owner = Owner.create(name: name)
+        assert_equal Encoding::ASCII_8BIT, name.encoding
+      end
+
       def test_execute
         @conn.execute "INSERT INTO items (number) VALUES (10)"
         records = @conn.execute "SELECT * FROM items"