diff --git a/src/util/hass-attributes-util.js b/src/util/hass-attributes-util.js
index e6d6a7e322..760eaed3bb 100644
--- a/src/util/hass-attributes-util.js
+++ b/src/util/hass-attributes-util.js
@@ -45,6 +45,7 @@ hassAttributeUtil.DOMAIN_DEVICE_CLASS = {
     "pressure",
     "power",
     "signal_strength",
+    "timestamp",
   ],
   switch: ["switch", "outlet"],
 };