diff --git a/lib/extension/networkMap.js b/lib/extension/networkMap.js
index efb69e2d0..0dd1b1003 100644
--- a/lib/extension/networkMap.js
+++ b/lib/extension/networkMap.js
@@ -74,7 +74,7 @@ class NetworkMap extends BaseExtension {
             let lastSeen = 'unknown';
             const date = device.type === 'Coordinator' ? Date.now() : device.lastSeen;
             if (date) {
-                lastSeen = utils.formatDate(date, 'ISO_8601_local', null);
+                lastSeen = utils.formatDate(date, 'ISO_8601_local');
             }
 
             labels.push(lastSeen);
diff --git a/lib/util/utils.js b/lib/util/utils.js
index 2f3a9445b..c8459ddd8 100644
--- a/lib/util/utils.js
+++ b/lib/util/utils.js
@@ -68,7 +68,7 @@ async function getZigbee2mqttVersion() {
     });
 }
 
-function formatDate(date, type, _default) {
+function formatDate(date, type) {
     let result;
 
     switch (type) {
@@ -82,8 +82,7 @@ function formatDate(date, type, _default) {
         result = date;
         break;
     default:
-        result = _default;
-        break;
+        throw new Error(`Unsupported type '${type}'`);
     }
 
     return result;
@@ -122,6 +121,6 @@ module.exports = {
     isIkeaTradfriDevice: (device) => ikeaTradfriManufacturerID.includes(device.manufacturerID),
     isRouter: (device) => device.type === 'Router' && !forceEndDevice.includes(device.modelID),
     isBatteryPowered: (device) => device.powerSource && device.powerSource === 'Battery',
-    formatDate: (date, type, _default=null) => formatDate(date, type, _default),
+    formatDate: (date, type) => formatDate(date, type),
     equalsPartial,
 };
diff --git a/test/stub/data.js b/test/stub/data.js
index 916e701bd..0bed9f47e 100644
--- a/test/stub/data.js
+++ b/test/stub/data.js
@@ -52,7 +52,6 @@ function writeDefaultConfiguration() {
                 friendly_name: "button_double_key_interviewing"
             },
             "0x0017880104e45540": {
-                retain: false,
                 friendly_name: "ikea_onoff"
             },
             '0x000b57fffec6a5b7': {
diff --git a/test/utils.test.js b/test/utils.test.js
index 488889b37..3ffc0627a 100644
--- a/test/utils.test.js
+++ b/test/utils.test.js
@@ -50,4 +50,9 @@ describe('Utils', () => {
         expect(utils.formatDate(date, 'ISO_8601_local').endsWith('+01:00')).toBeTruthy();
         Date.prototype.getTimezoneOffset = getTimezoneOffset;
     })
+
+    it('Throw exception when formating with invalid date', async () => {
+        var date = new Date('August 19, 1975 23:15:30 UTC+00:00');
+        expect(() => utils.formatDate(date, 'invalid', 1)).toThrowError("Unsupported type 'invalid'")
+    })
 });