diff --git a/app/models/agents/mqtt_agent.rb b/app/models/agents/mqtt_agent.rb
index 73a889c9..e60c575d 100644
--- a/app/models/agents/mqtt_agent.rb
+++ b/app/models/agents/mqtt_agent.rb
@@ -115,15 +115,26 @@ module Agents
 
 
     def check
+      last_message = memory['last_message']
+
       mqtt_client.connect do |c|
         begin
           Timeout.timeout((interpolated['max_read_time'].presence || 15).to_i) {
-            c.get(interpolated['topic']) do |topic, message|
+            c.get_packet(interpolated['topic']) do |packet|
+              topic, payload = message = [packet.topic, packet.payload]
 
-              # A lot of services generate JSON. Try that first
-              payload = JSON.parse(message) rescue message
+              # Ignore a message if it is previously received
+              next if (packet.retain || packet.duplicate) && message == last_message
 
-              create_event :payload => {
+              last_message = message
+
+              # A lot of services generate JSON, so try that.
+              begin
+                payload = JSON.parse(payload)
+              rescue
+              end
+
+              create_event payload: {
                 'topic' => topic,
                 'message' => payload,
                 'time' => Time.now.to_i
@@ -133,6 +144,10 @@ module Agents
         rescue Timeout::Error
         end
       end
+
+      # Remember the last original (non-retain, non-duplicate) message
+      self.memory['last_message'] = last_message
+      save!
     end
 
   end
diff --git a/spec/models/agents/mqtt_agent_spec.rb b/spec/models/agents/mqtt_agent_spec.rb
index 0b070102..953e4a9f 100644
--- a/spec/models/agents/mqtt_agent_spec.rb
+++ b/spec/models/agents/mqtt_agent_spec.rb
@@ -8,7 +8,6 @@ describe Agents::MqttAgent do
     @error_log = StringIO.new
 
     @server = MQTT::FakeServer.new(41234, '127.0.0.1')
-    @server.just_one = true
     @server.logger = Logger.new(@error_log)
     @server.logger.level = Logger::DEBUG
     @server.start
@@ -34,7 +33,14 @@ describe Agents::MqttAgent do
   end
 
   describe "#check" do
-    it "should check that initial run creates an event" do
+    it "should create events in the initial run" do
+      expect { @checker.check }.to change { Event.count }.by(2)
+    end
+
+    it "should ignore retained messages that are previously received" do
+      expect { @checker.check }.to change { Event.count }.by(2)
+      expect { @checker.check }.to change { Event.count }.by(1)
+      expect { @checker.check }.to change { Event.count }.by(1)
       expect { @checker.check }.to change { Event.count }.by(2)
     end
   end
diff --git a/spec/support/fake_mqtt_server.rb b/spec/support/fake_mqtt_server.rb
index 39f8db74..71c3ab1f 100644
--- a/spec/support/fake_mqtt_server.rb
+++ b/spec/support/fake_mqtt_server.rb
@@ -52,7 +52,9 @@ class MQTT::FakeServer
     @port = @socket.addr[1]
     @thread ||= Thread.new do
       logger.info "Started a fake MQTT server on #{@address}:#{@port}"
+      @times = 0
       loop do
+        @times += 1
         # Wait for a client to connect
         client = @socket.accept
         @pings_received = 0
@@ -103,16 +105,33 @@ class MQTT::FakeServer
             :granted_qos => 0
           )
           topic = packet.topics[0][0]
-          client.write MQTT::Packet::Publish.new(
-            :topic => topic,
-            :payload => "hello #{topic}",
-            :retain => true
-          )
-          client.write MQTT::Packet::Publish.new(
-            :topic => topic,
-            :payload => "did you know about #{topic}",
-            :retain => true
-          )
+          case @times
+          when 1, ->x { x >= 3 }
+            # Deliver retained messages
+            client.write MQTT::Packet::Publish.new(
+              :topic => topic,
+              :payload => "did you know about #{topic}",
+              :retain => true
+            )
+            client.write MQTT::Packet::Publish.new(
+              :topic => topic,
+              :payload => "hello #{topic}",
+              :retain => true
+            )
+          when 2
+            # Deliver a still retained message
+            client.write MQTT::Packet::Publish.new(
+              :topic => topic,
+              :payload => "hello #{topic}",
+              :retain => true
+            )
+            # Deliver a fresh message
+            client.write MQTT::Packet::Publish.new(
+              :topic => topic,
+              :payload => "did you know about #{topic}",
+              :retain => false
+            )
+          end
 
         when MQTT::Packet::Pingreq
           client.write MQTT::Packet::Pingresp.new
@@ -134,4 +153,4 @@ if __FILE__ == $0
   server = MQTT::FakeServer.new(MQTT::DEFAULT_PORT)
   server.logger.level = Logger::DEBUG
   server.run
-end
\ No newline at end of file
+end