diff --git a/src/main/java/org/elasticsearch/discovery/zen/ping/unicast/UnicastZenPing.java b/src/main/java/org/elasticsearch/discovery/zen/ping/unicast/UnicastZenPing.java
index d7eadc28e6f..63e49747ff8 100644
--- a/src/main/java/org/elasticsearch/discovery/zen/ping/unicast/UnicastZenPing.java
+++ b/src/main/java/org/elasticsearch/discovery/zen/ping/unicast/UnicastZenPing.java
@@ -342,7 +342,17 @@ public class UnicastZenPing extends AbstractLifecycleComponent<ZenPing> implemen
                         if (responses == null) {
                             logger.warn("received ping response {} with no matching id [{}]", pingResponse, response.id);
                         } else {
-                            responses.put(pingResponse.target(), pingResponse);
+                            PingResponse existingResponse = responses.get(pingResponse.target());
+                            if (existingResponse == null) {
+                                responses.put(pingResponse.target(), pingResponse);
+                            } else {
+                                // try and merge the best ping response for it, i.e. if the new one
+                                // doesn't have the master node set, and the existing one does, then
+                                // the existing one is better, so we keep it
+                                if (pingResponse.master() != null) {
+                                    responses.put(pingResponse.target(), pingResponse);
+                                }
+                            }
                         }
                     }
                 } finally {
diff --git a/src/test/java/org/elasticsearch/cluster/ZenUnicastDiscoveryTests.java b/src/test/java/org/elasticsearch/cluster/ZenUnicastDiscoveryTests.java
new file mode 100644
index 00000000000..b05e4101751
--- /dev/null
+++ b/src/test/java/org/elasticsearch/cluster/ZenUnicastDiscoveryTests.java
@@ -0,0 +1,112 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.cluster;
+
+import org.apache.lucene.util.LuceneTestCase;
+import org.elasticsearch.action.admin.cluster.health.ClusterHealthResponse;
+import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.common.Priority;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.util.concurrent.AtomicArray;
+import org.elasticsearch.test.ElasticsearchIntegrationTest;
+import org.elasticsearch.test.junit.annotations.TestLogging;
+import org.junit.Test;
+
+import java.util.concurrent.CountDownLatch;
+
+import static org.elasticsearch.common.settings.ImmutableSettings.settingsBuilder;
+import static org.hamcrest.Matchers.equalTo;
+
+/**
+ */
+@LuceneTestCase.Slow
+@ElasticsearchIntegrationTest.ClusterScope(scope = ElasticsearchIntegrationTest.Scope.TEST, numNodes = 0)
+public class ZenUnicastDiscoveryTests extends ElasticsearchIntegrationTest {
+
+    @Test
+    @TestLogging("discovery.zen:TRACE")
+    // The bug zen unicast ping override bug, may rarely manifest itself, it is very timing dependant.
+    // Without the fix in UnicastZenPing, this test fails roughly 1 out of 10 runs from the command line.
+    public void testMasterElectionNotMissed() throws Exception {
+        final Settings settings = settingsBuilder()
+                // Failure only manifests if multicast ping is disabled!
+                .put("discovery.zen.ping.multicast.ping.enabled", false)
+                .put("discovery.zen.minimum_master_nodes", 2)
+                // Can't use this, b/c at the moment all node will only ping localhost:9300
+//                .put("discovery.zen.ping.unicast.hosts", "localhost")
+                .put("discovery.zen.ping.unicast.hosts", "localhost:15300,localhost:15301,localhost:15302")
+                .put("transport.tcp.port", "15300-15400")
+                .build();
+
+        final CountDownLatch latch = new CountDownLatch(3);
+        final AtomicArray<String> nodes = new AtomicArray<String>(3);
+        Runnable r1 = new Runnable() {
+
+            @Override
+            public void run() {
+                logger.info("--> start first node");
+                nodes.set(0, cluster().startNode(settings));
+                latch.countDown();
+            }
+        };
+        new Thread(r1).start();
+
+        sleep(between(500, 3000));
+        Runnable r2 = new Runnable() {
+
+            @Override
+            public void run() {
+                logger.info("--> start second node");
+                nodes.set(1, cluster().startNode(settings));
+                latch.countDown();
+            }
+        };
+        new Thread(r2).start();
+
+
+        sleep(between(500, 3000));
+        Runnable r3 = new Runnable() {
+
+            @Override
+            public void run() {
+                logger.info("--> start third node");
+                nodes.set(2, cluster().startNode(settings));
+                latch.countDown();
+            }
+        };
+        new Thread(r3).start();
+        latch.await();
+
+        ClusterHealthResponse clusterHealthResponse = client().admin().cluster().prepareHealth().setWaitForEvents(Priority.LANGUID).setWaitForNodes("3").execute().actionGet();
+        assertThat(clusterHealthResponse.isTimedOut(), equalTo(false));
+
+        DiscoveryNode masterDiscoNode = null;
+        for (String node : nodes.toArray(new String[3])) {
+            ClusterState state = cluster().client(node).admin().cluster().prepareState().setLocal(true).execute().actionGet().getState();
+            assertThat(state.nodes().size(), equalTo(3));
+            if (masterDiscoNode == null) {
+                masterDiscoNode = state.nodes().masterNode();
+            } else {
+                assertThat(masterDiscoNode.equals(state.nodes().masterNode()), equalTo(true));
+            }
+        }
+    }
+
+}