diff --git a/homeassistant/components/cert_expiry/sensor.py b/homeassistant/components/cert_expiry/sensor.py
index b564cff7338..2cd5c9abc8e 100644
--- a/homeassistant/components/cert_expiry/sensor.py
+++ b/homeassistant/components/cert_expiry/sensor.py
@@ -67,6 +67,11 @@ class SSLCertificate(Entity):
         """Return the name of the sensor."""
         return self._name
 
+    @property
+    def unique_id(self):
+        """Return a unique id for the sensor."""
+        return f"{self.server_name}:{self.server_port}"
+
     @property
     def unit_of_measurement(self):
         """Return the unit this state is expressed in."""