7 Property operating expenses
| | 2017 | 2016 |
Taxes | 1,663 | 1,591 |
Insurance | 205 | 80 |
Maintenance | 6,971 | 3,530 |
Valuation fees | 113 | 55 |
Property management fees | 1,046 | 904 |
Letting and lease renewal fees | 2,731 | 3,288 |
Other operating expenses | 4,596 | 3,602 |
Addition to provision for bad debts | (288) | 275 |
Total property operating expenses | 17,037 | 13,325 |
In 2017, € 0.2 million (2016: € 0.2 million) of the maintenance expenses related to unlet properties.