diff --git a/java/google/registry/model/registry/Registry.java b/java/google/registry/model/registry/Registry.java
index f93ba9cc2..cc5b10985 100644
--- a/java/google/registry/model/registry/Registry.java
+++ b/java/google/registry/model/registry/Registry.java
@@ -18,10 +18,10 @@ import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Predicates.equalTo;
 import static com.google.common.base.Predicates.not;
+import static com.google.common.collect.Iterables.getOnlyElement;
 import static google.registry.config.RegistryConfig.getSingletonCacheRefreshDuration;
 import static google.registry.model.common.EntityGroupRoot.getCrossTldKey;
 import static google.registry.model.ofy.ObjectifyService.ofy;
-import static google.registry.util.CollectionUtils.isNullOrEmpty;
 import static google.registry.util.CollectionUtils.nullToEmptyImmutableCopy;
 import static google.registry.util.DateTimeUtils.END_OF_TIME;
 import static google.registry.util.DateTimeUtils.START_OF_TIME;
@@ -290,8 +290,8 @@ public class Registry extends ImmutableObject implements Buildable {
 
   @OnLoad
   public void migrateDnsWriters() {
-    if (isNullOrEmpty(dnsWriters)) {
-      dnsWriters = ImmutableSet.of(dnsWriter);
+    if (dnsWriter == null) {
+      dnsWriter = getOnlyElement(dnsWriters);
     }
   }
 
@@ -613,7 +613,7 @@ public class Registry extends ImmutableObject implements Buildable {
 
   @Deprecated
   public String getDnsWriter() {
-    return dnsWriter;
+    return getOnlyElement(dnsWriters);
   }
 
   public ImmutableSet<String> getDnsWriters() {
@@ -702,13 +702,13 @@ public class Registry extends ImmutableObject implements Buildable {
       return this;
     }
 
-    public Builder setDnsWriter(String dnsWriter) {
-      getInstance().dnsWriter = checkArgumentNotNull(dnsWriter);
-      getInstance().dnsWriters = ImmutableSet.of(dnsWriter);
+    public Builder setDnsWriters(ImmutableSet<String> dnsWriters) {
+      checkArgument(dnsWriters.size() == 1, "Multiple DNS writers are not yet supported");
+      getInstance().dnsWriters = dnsWriters;
+      getInstance().dnsWriter = getOnlyElement(dnsWriters);
       return this;
     }
 
-
     public Builder setAddGracePeriodLength(Duration addGracePeriodLength) {
       checkArgument(addGracePeriodLength.isLongerThan(Duration.ZERO),
           "addGracePeriodLength must be non-zero");
diff --git a/java/google/registry/tools/CreateOrUpdateTldCommand.java b/java/google/registry/tools/CreateOrUpdateTldCommand.java
index 47bda613e..d8056e7ea 100644
--- a/java/google/registry/tools/CreateOrUpdateTldCommand.java
+++ b/java/google/registry/tools/CreateOrUpdateTldCommand.java
@@ -393,7 +393,7 @@ abstract class CreateOrUpdateTldCommand extends MutatingCommand {
               dnsWriterNames.contains(dnsWriter.get()),
               "The DNS writer '%s' doesn't exist",
               dnsWriter.get());
-          builder.setDnsWriter(dnsWriter.get());
+          builder.setDnsWriters(ImmutableSet.of(dnsWriter.get()));
       }
 
       if (lrpPeriod != null) {
diff --git a/javatests/google/registry/dns/PublishDnsUpdatesActionTest.java b/javatests/google/registry/dns/PublishDnsUpdatesActionTest.java
index 479702c49..3f28cc90f 100644
--- a/javatests/google/registry/dns/PublishDnsUpdatesActionTest.java
+++ b/javatests/google/registry/dns/PublishDnsUpdatesActionTest.java
@@ -63,7 +63,8 @@ public class PublishDnsUpdatesActionTest {
   public void setUp() throws Exception {
     inject.setStaticField(Ofy.class, "clock", clock);
     createTld("xn--q9jyb4c");
-    persistResource(Registry.get("xn--q9jyb4c").asBuilder().setDnsWriter("mock").build());
+    persistResource(
+        Registry.get("xn--q9jyb4c").asBuilder().setDnsWriters(ImmutableSet.of("mock")).build());
     DomainResource domain1 = persistActiveDomain("example.xn--q9jyb4c");
     persistActiveSubordinateHost("ns1.example.xn--q9jyb4c", domain1);
     persistActiveSubordinateHost("ns2.example.xn--q9jyb4c", domain1);
diff --git a/javatests/google/registry/model/registry/label/PremiumListUtilsTest.java b/javatests/google/registry/model/registry/label/PremiumListUtilsTest.java
index 5e56f0b54..da5a39749 100644
--- a/javatests/google/registry/model/registry/label/PremiumListUtilsTest.java
+++ b/javatests/google/registry/model/registry/label/PremiumListUtilsTest.java
@@ -37,6 +37,7 @@ import static org.joda.time.Duration.standardMinutes;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.googlecode.objectify.Key;
 import com.googlecode.objectify.VoidWork;
 import google.registry.dns.writer.VoidDnsWriter;
@@ -98,7 +99,7 @@ public class PremiumListUtilsTest {
         new Registry.Builder()
             .setTldStr("ghost")
             .setPremiumPricingEngine(StaticPremiumListPricingEngine.NAME)
-            .setDnsWriter(VoidDnsWriter.NAME)
+            .setDnsWriters(ImmutableSet.of(VoidDnsWriter.NAME))
             .build());
     assertThat(Registry.get("ghost").getPremiumList()).isNull();
     assertThat(getPremiumPrice("blah", Registry.get("ghost"))).isAbsent();
diff --git a/javatests/google/registry/testing/DatastoreHelper.java b/javatests/google/registry/testing/DatastoreHelper.java
index 9ec3cac64..1fdcd72da 100644
--- a/javatests/google/registry/testing/DatastoreHelper.java
+++ b/javatests/google/registry/testing/DatastoreHelper.java
@@ -268,7 +268,7 @@ public class DatastoreHelper {
         // Always set a default premium list. Tests that don't want it can delete it.
         .setPremiumList(persistPremiumList(tld, DEFAULT_PREMIUM_LIST_CONTENTS.get()))
         .setPremiumPricingEngine(StaticPremiumListPricingEngine.NAME)
-        .setDnsWriter(VoidDnsWriter.NAME)
+        .setDnsWriters(ImmutableSet.of(VoidDnsWriter.NAME))
         .build();
   }
 
diff --git a/javatests/google/registry/tools/CreateTldCommandTest.java b/javatests/google/registry/tools/CreateTldCommandTest.java
index 02f5ad477..c057c0794 100644
--- a/javatests/google/registry/tools/CreateTldCommandTest.java
+++ b/javatests/google/registry/tools/CreateTldCommandTest.java
@@ -66,7 +66,7 @@ public class CreateTldCommandTest extends CommandTestCase<CreateTldCommand> {
     assertThat(registry.getAddGracePeriodLength()).isEqualTo(Registry.DEFAULT_ADD_GRACE_PERIOD);
     assertThat(registry.getCreationTime()).isIn(Range.closed(before, after));
     assertThat(registry.getDomainCreateRestricted()).isFalse();
-    assertThat(registry.getDnsWriter()).isEqualTo("FooDnsWriter");
+    assertThat(registry.getDnsWriters()).containsExactly("FooDnsWriter");
     assertThat(registry.getTldState(registry.getCreationTime())).isEqualTo(TldState.PREDELEGATION);
     assertThat(registry.getRedemptionGracePeriodLength())
         .isEqualTo(Registry.DEFAULT_REDEMPTION_GRACE_PERIOD);