diff --git a/java/google/registry/proxy/ProxyConfig.java b/java/google/registry/proxy/ProxyConfig.java
index f040e3769..11213cef8 100644
--- a/java/google/registry/proxy/ProxyConfig.java
+++ b/java/google/registry/proxy/ProxyConfig.java
@@ -17,6 +17,7 @@ package google.registry.proxy;
 import static google.registry.config.YamlUtils.getConfigSettings;
 import static google.registry.util.ResourceUtils.readResourceUtf8;
 
+import com.google.common.base.Ascii;
 import java.util.List;
 
 /** The POJO that YAML config files are deserialized into. */
@@ -120,7 +121,8 @@ public class ProxyConfig {
     String customYaml =
         readResourceUtf8(
             ProxyConfig.class,
-            String.format(CUSTOM_CONFIG_FORMATTER, env.name().toLowerCase().replace("_", "-")));
+            String.format(
+                CUSTOM_CONFIG_FORMATTER, Ascii.toLowerCase(env.name()).replace("_", "-")));
     return getConfigSettings(defaultYaml, customYaml, ProxyConfig.class);
   }
 }
diff --git a/java/google/registry/tools/GetAppliedLabelsCommand.java b/java/google/registry/tools/GetAppliedLabelsCommand.java
index c32eb8e53..144dbf6dd 100644
--- a/java/google/registry/tools/GetAppliedLabelsCommand.java
+++ b/java/google/registry/tools/GetAppliedLabelsCommand.java
@@ -23,6 +23,7 @@ import static java.nio.charset.StandardCharsets.UTF_8;
 import com.beust.jcommander.Parameter;
 import com.beust.jcommander.Parameters;
 import com.beust.jcommander.internal.Sets;
+import com.google.common.base.Ascii;
 import google.registry.model.domain.DomainApplication;
 import google.registry.model.domain.launch.ApplicationStatus;
 import google.registry.tools.Command.RemoteApiCommand;
@@ -58,7 +59,7 @@ final class GetAppliedLabelsCommand implements RemoteApiCommand {
     for (String label : getDomainApplicationMap(assertTldExists(tld))) {
       label = label.substring(0, label.lastIndexOf('.'));
       try {
-        lines.add(Idn.toUnicode(label.toLowerCase()));
+        lines.add(Idn.toUnicode(Ascii.toLowerCase(label)));
       } catch (IllegalArgumentException e) {
         // An invalid punycode label that we need to reject later.
         lines.add(label + " (invalid)");
diff --git a/java/google/registry/util/NetworkUtils.java b/java/google/registry/util/NetworkUtils.java
index bfe6ada2a..33e018fed 100644
--- a/java/google/registry/util/NetworkUtils.java
+++ b/java/google/registry/util/NetworkUtils.java
@@ -17,6 +17,7 @@ package google.registry.util;
 import static com.google.common.base.Preconditions.checkArgument;
 import static google.registry.util.CollectionUtils.union;
 
+import com.google.common.base.Ascii;
 import com.google.common.collect.ImmutableSet;
 import java.io.IOException;
 import java.net.Inet6Address;
@@ -72,7 +73,7 @@ public final class NetworkUtils {
    */
   public static String getCanonicalHostName() {
     try {
-      return getExternalAddressOfLocalSystem().getCanonicalHostName().toLowerCase();
+      return Ascii.toLowerCase(getExternalAddressOfLocalSystem().getCanonicalHostName());
     } catch (UnknownHostException e) {
       throw new RuntimeException(e);
     }