diff --git a/helios-services/src/main/java/com/spotify/helios/agent/AgentZooKeeperRegistrar.java b/helios-services/src/main/java/com/spotify/helios/agent/AgentZooKeeperRegistrar.java
index 3c657f05d..59ab32288 100644
--- a/helios-services/src/main/java/com/spotify/helios/agent/AgentZooKeeperRegistrar.java
+++ b/helios-services/src/main/java/com/spotify/helios/agent/AgentZooKeeperRegistrar.java
@@ -102,19 +102,26 @@ public void tryToRegister(ZooKeeperClient client)
       final byte[] bytes = client.getData(idPath);
       final String existingId = bytes == null ? "" : new String(bytes, UTF_8);
       if (!id.equals(existingId)) {
-        final long mtime = client.stat(hostInfoPath).getMtime();
-        if ((clock.now().getMillis() - mtime) < zooKeeperRegistrationTtlMillis) {
-          final String message = format("Another agent already registered as '%s' " +
-                                        "(local=%s remote=%s).", name, id, existingId);
-          log.error(message);
-          agentService.stopAsync();
-          return;
+        final Stat hostInfoStat = client.stat(hostInfoPath);
+        if (hostInfoStat != null) {
+          final long mtime = hostInfoStat.getMtime();
+          if ((clock.now().getMillis() - mtime) < zooKeeperRegistrationTtlMillis) {
+            final String message = format("Another agent already registered as '%s' " +
+                                          "(local=%s remote=%s).", name, id, existingId);
+            log.error(message);
+            agentService.stopAsync();
+            return;
+          }
+
+          log.info("Another agent has already registered as '{}', but its ID node was last " +
+                   "updated more than {} milliseconds ago. I\'m deregistering the agent with the "
+                   + "old ID of {} and replacing it with this new agent with ID '{}'.",
+                   name, zooKeeperRegistrationTtlMillis, existingId, id);
+        } else {
+          log.info("Another agent has registered as '{}', but it never updated '{}' in ZooKeeper. "
+                   + "I'll assume it's dead and deregister it.", name, hostInfoPath);
         }
 
-        log.info("Another agent has already registered as '{}', but its ID node was last " +
-                 "updated more than {} milliseconds ago. I\'m deregistering the agent with the "
-                 + "old ID of {} and replacing it with this new agent with ID '{}'.",
-                 name, zooKeeperRegistrationTtlMillis, existingId, id);
         ZooKeeperRegistrarUtil.deregisterHost(client, name);
         ZooKeeperRegistrarUtil.registerHost(client, idPath, name, id);
       } else {
diff --git a/helios-system-tests/src/main/java/com/spotify/helios/system/DeregisterTest.java b/helios-system-tests/src/main/java/com/spotify/helios/system/DeregisterTest.java
index 49f8d9e28..60a031b04 100644
--- a/helios-system-tests/src/main/java/com/spotify/helios/system/DeregisterTest.java
+++ b/helios-system-tests/src/main/java/com/spotify/helios/system/DeregisterTest.java
@@ -40,6 +40,8 @@
 import org.junit.Rule;
 import org.junit.Test;
 
+import java.util.concurrent.TimeoutException;
+
 import static com.spotify.helios.common.descriptors.Goal.START;
 import static com.spotify.helios.common.descriptors.HostStatus.Status.DOWN;
 import static com.spotify.helios.common.descriptors.HostStatus.Status.UP;
@@ -120,6 +122,8 @@ public void testRegistrationResolution() throws Exception {
     final HostStatus hostStatus1 =
         awaitHostStatusWithLabels(client, host, UP, LONG_WAIT_SECONDS, SECONDS);
     assertThat(hostStatus1.getLabels(), Matchers.hasEntry("num", "1"));
+    // Wait for agent to be UP and report HostInfo
+    awaitHostStatusWithHostInfo(client, host, UP, LONG_WAIT_SECONDS, SECONDS);
 
     // Kill off agent
     agent.stopAsync().awaitTerminated();
@@ -137,17 +141,18 @@ public void testRegistrationResolution() throws Exception {
     assertThat(hostStatus2.getLabels(), Matchers.hasEntry("num", "2"));
   }
 
-  @Test(expected = IllegalStateException.class)
+  @Test(expected = TimeoutException.class)
   public void testRegistrationResolutionTtlNotExpired() throws Exception {
     startDefaultMaster();
-    final String host = testHost() + "2";
+    final String host = testHost();
     AgentMain agent = startDefaultAgent(host);
 
     final HeliosClient client = defaultClient();
 
     // Wait for agent to come up
     awaitHostRegistered(client, host, LONG_WAIT_SECONDS, SECONDS);
-    awaitHostStatus(client, host, UP, LONG_WAIT_SECONDS, SECONDS);
+    // Wait for agent to be UP and report HostInfo
+    awaitHostStatusWithHostInfo(client, host, UP, LONG_WAIT_SECONDS, SECONDS);
 
     // Kill off agent
     agent.stopAsync().awaitTerminated();
@@ -157,7 +162,13 @@ public void testRegistrationResolutionTtlNotExpired() throws Exception {
     resetAgentStateDir();
 
     // Set TTL to a large number so new agent will not deregister previous one.
-    // This should throw IllegalStateException as this agent will fail to start as it can't register
-    startDefaultAgent(host, "--zk-registration-ttl", "9999");
+    // This might throw IllegalStateException as this agent will fail to start since it can't
+    // register. This exception sometimes occurs and sometimes doesn't. We ignore that and
+    // instead check for the TimeoutException while polling for it being UP.
+    try {
+      startDefaultAgent(host, "--zk-registration-ttl", "9999");
+    } catch (IllegalStateException ignored) {
+    }
+    awaitHostStatus(client, host, UP, 10, SECONDS);
   }
 }
diff --git a/helios-system-tests/src/main/java/com/spotify/helios/system/SystemTestBase.java b/helios-system-tests/src/main/java/com/spotify/helios/system/SystemTestBase.java
index 365ce155f..92867d4ae 100644
--- a/helios-system-tests/src/main/java/com/spotify/helios/system/SystemTestBase.java
+++ b/helios-system-tests/src/main/java/com/spotify/helios/system/SystemTestBase.java
@@ -959,6 +959,22 @@ public HostStatus call() throws Exception {
     });
   }
 
+  protected HostStatus awaitHostStatusWithHostInfo(final HeliosClient client, final String host,
+                                                   final HostStatus.Status status,
+                                                   final int timeout,
+                                                   final TimeUnit timeUnit) throws Exception {
+    return Polling.await(timeout, timeUnit, new Callable<HostStatus>() {
+      @Override
+      public HostStatus call() throws Exception {
+        final HostStatus hostStatus = getOrNull(client.hostStatus(host));
+        if (hostStatus == null || hostStatus.getHostInfo() == null) {
+          return null;
+        }
+        return (hostStatus.getStatus() == status) ? hostStatus : null;
+      }
+    });
+  }
+
   protected TaskStatus awaitTaskState(final JobId jobId, final String host,
                                       final TaskStatus.State state) throws Exception {
     return Polling.await(LONG_WAIT_SECONDS, SECONDS, new Callable<TaskStatus>() {