diff --git a/java/google/registry/flows/host/HostFlowUtils.java b/java/google/registry/flows/host/HostFlowUtils.java
index 805f89689..2780f3095 100644
--- a/java/google/registry/flows/host/HostFlowUtils.java
+++ b/java/google/registry/flows/host/HostFlowUtils.java
@@ -47,11 +47,11 @@ public class HostFlowUtils {
     if (!name.equals(hostNameLowerCase)) {
       throw new HostNameNotLowerCaseException(hostNameLowerCase);
     }
-    String hostNamePunyCoded = Idn.toASCII(name);
-    if (!name.equals(hostNamePunyCoded)) {
-      throw new HostNameNotPunyCodedException(hostNamePunyCoded);
-    }
     try {
+      String hostNamePunyCoded = Idn.toASCII(name);
+      if (!name.equals(hostNamePunyCoded)) {
+        throw new HostNameNotPunyCodedException(hostNamePunyCoded);
+      }
       InternetDomainName hostName = InternetDomainName.from(name);
       if (!name.equals(hostName.toString())) {
         throw new HostNameNotNormalizedException(hostName.toString());
diff --git a/javatests/google/registry/flows/host/HostFlowUtilsTest.java b/javatests/google/registry/flows/host/HostFlowUtilsTest.java
new file mode 100644
index 000000000..1c345651f
--- /dev/null
+++ b/javatests/google/registry/flows/host/HostFlowUtilsTest.java
@@ -0,0 +1,76 @@
+// Copyright 2016 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed 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 google.registry.flows.host;
+
+import static google.registry.flows.host.HostFlowUtils.validateHostName;
+
+import com.google.common.base.Strings;
+import google.registry.flows.host.HostFlowUtils.HostNameNotLowerCaseException;
+import google.registry.flows.host.HostFlowUtils.HostNameNotNormalizedException;
+import google.registry.flows.host.HostFlowUtils.HostNameNotPunyCodedException;
+import google.registry.flows.host.HostFlowUtils.HostNameTooLongException;
+import google.registry.flows.host.HostFlowUtils.HostNameTooShallowException;
+import google.registry.flows.host.HostFlowUtils.InvalidHostNameException;
+import google.registry.testing.AppEngineRule;
+import google.registry.testing.ExceptionRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link HostFlowUtils}. */
+@RunWith(JUnit4.class)
+public class HostFlowUtilsTest {
+
+  @Rule public final ExceptionRule thrown = new ExceptionRule();
+
+  @Rule public final AppEngineRule appEngine = AppEngineRule.builder().withDatastore().build();
+
+  @Test
+  public void test_validateHostName_hostNameTooLong() throws Exception {
+    thrown.expect(HostNameTooLongException.class);
+    validateHostName(Strings.repeat("na", 200) + ".wat.man");
+  }
+
+  @Test
+  public void test_validateHostName_hostNameNotLowerCase() throws Exception {
+    thrown.expect(HostNameNotLowerCaseException.class);
+    validateHostName("NA.CAPS.TLD");
+  }
+
+  @Test
+  public void test_validateHostName_hostNameNotPunyCoded() throws Exception {
+    thrown.expect(HostNameNotPunyCodedException.class);
+    validateHostName("motörhead.death.metal");
+  }
+
+  @Test
+  public void test_validateHostName_hostNameNotNormalized() throws Exception {
+    thrown.expect(HostNameNotNormalizedException.class);
+    validateHostName("root.node.yeah.");
+  }
+
+  @Test
+  public void test_validateHostName_hostNameHasLeadingHyphen() throws Exception {
+    thrown.expect(InvalidHostNameException.class);
+    validateHostName("-giga.mega.tld");
+  }
+
+  @Test
+  public void test_validateHostName_hostNameTooShallow() throws Exception {
+    thrown.expect(HostNameTooShallowException.class);
+    validateHostName("domain.tld");
+  }
+}