diff --git a/server/src/main/java/org/elasticsearch/bootstrap/BootstrapChecks.java b/server/src/main/java/org/elasticsearch/bootstrap/BootstrapChecks.java
index c34d84d7883..90b1ef56237 100644
--- a/server/src/main/java/org/elasticsearch/bootstrap/BootstrapChecks.java
+++ b/server/src/main/java/org/elasticsearch/bootstrap/BootstrapChecks.java
@@ -739,6 +739,11 @@ final class BootstrapChecks {
     static class DiscoveryConfiguredCheck implements BootstrapCheck {
         @Override
         public BootstrapCheckResult check(BootstrapContext context) {
+            if (DiscoveryModule.ZEN_DISCOVERY_TYPE.equals(DiscoveryModule.DISCOVERY_TYPE_SETTING.get(context.settings()))) {
+                return BootstrapCheckResult.failure(String.format(Locale.ROOT,
+                    "discovery type [%s] is unsuitable for production use", DiscoveryModule.ZEN_DISCOVERY_TYPE));
+            }
+
             if (DiscoveryModule.ZEN2_DISCOVERY_TYPE.equals(DiscoveryModule.DISCOVERY_TYPE_SETTING.get(context.settings())) == false) {
                 return BootstrapCheckResult.success();
             }
diff --git a/server/src/main/java/org/elasticsearch/discovery/DiscoveryModule.java b/server/src/main/java/org/elasticsearch/discovery/DiscoveryModule.java
index 6cccf9aea3d..fc6218f70f5 100644
--- a/server/src/main/java/org/elasticsearch/discovery/DiscoveryModule.java
+++ b/server/src/main/java/org/elasticsearch/discovery/DiscoveryModule.java
@@ -19,8 +19,9 @@
 
 package org.elasticsearch.discovery;
 
-import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.elasticsearch.Assertions;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.coordination.Coordinator;
 import org.elasticsearch.cluster.coordination.ElectionStrategy;
@@ -67,7 +68,7 @@ import static org.elasticsearch.node.Node.NODE_NAME_SETTING;
 public class DiscoveryModule {
     private static final Logger logger = LogManager.getLogger(DiscoveryModule.class);
 
-    public static final String ZEN_DISCOVERY_TYPE = "legacy-zen";
+    public static final String ZEN_DISCOVERY_TYPE = "legacy-zen-for-testing-only-do-not-use";
     public static final String ZEN2_DISCOVERY_TYPE = "zen";
 
     public static final String SINGLE_NODE_DISCOVERY_TYPE = "single-node";
@@ -155,7 +156,7 @@ public class DiscoveryModule {
                 transportService, namedWriteableRegistry, allocationService, masterService, gatewayMetaState::getPersistedState,
                 seedHostsProvider, clusterApplier, joinValidators, new Random(Randomness.get().nextLong()), rerouteService,
                 electionStrategy, nodeHealthService);
-        } else if (ZEN_DISCOVERY_TYPE.equals(discoveryType)) {
+        } else if (Assertions.ENABLED && ZEN_DISCOVERY_TYPE.equals(discoveryType)) {
             discovery = new ZenDiscovery(settings, threadPool, transportService, namedWriteableRegistry, masterService, clusterApplier,
                 clusterSettings, seedHostsProvider, allocationService, joinValidators, rerouteService);
         } else {
diff --git a/server/src/test/java/org/elasticsearch/bootstrap/BootstrapChecksTests.java b/server/src/test/java/org/elasticsearch/bootstrap/BootstrapChecksTests.java
index 0bcef6ebc81..2b4d697271c 100644
--- a/server/src/test/java/org/elasticsearch/bootstrap/BootstrapChecksTests.java
+++ b/server/src/test/java/org/elasticsearch/bootstrap/BootstrapChecksTests.java
@@ -723,6 +723,9 @@ public class BootstrapChecksTests extends AbstractBootstrapCheckTestCase {
     public void testDiscoveryConfiguredCheck() throws NodeValidationException {
         final List<BootstrapCheck> checks = Collections.singletonList(new BootstrapChecks.DiscoveryConfiguredCheck());
 
+        final BootstrapContext zen1Context = createTestContext(Settings.builder()
+                .put(DiscoveryModule.DISCOVERY_TYPE_SETTING.getKey(), ZEN_DISCOVERY_TYPE).build(), Metadata.EMPTY_METADATA);
+
         final BootstrapContext zen2Context = createTestContext(Settings.builder()
             .put(DiscoveryModule.DISCOVERY_TYPE_SETTING.getKey(), ZEN2_DISCOVERY_TYPE).build(), Metadata.EMPTY_METADATA);
 
@@ -731,7 +734,11 @@ public class BootstrapChecksTests extends AbstractBootstrapCheckTestCase {
 
         // not enforced for non-zen2 discovery
         BootstrapChecks.check(createTestContext(Settings.builder().put(DiscoveryModule.DISCOVERY_TYPE_SETTING.getKey(),
-            randomFrom(ZEN_DISCOVERY_TYPE, "single-node", randomAlphaOfLength(5))).build(), Metadata.EMPTY_METADATA), true, checks);
+            randomFrom("single-node", randomAlphaOfLength(5))).build(), Metadata.EMPTY_METADATA), true, checks);
+
+        assertThat(expectThrows(NodeValidationException.class,
+                () -> BootstrapChecks.check(zen1Context, true, checks)),
+                hasToString(containsString("discovery type [legacy-zen-for-testing-only-do-not-use] is unsuitable for production use")));
 
         final NodeValidationException e = expectThrows(NodeValidationException.class,
             () -> BootstrapChecks.check(zen2Context, true, checks));