diff --git a/source/common/config/utility.cc b/source/common/config/utility.cc
index aa3d8cd80fe00..926362ff38535 100644
--- a/source/common/config/utility.cc
+++ b/source/common/config/utility.cc
@@ -25,15 +25,19 @@ void Utility::translateApiConfigSource(const std::string& cluster, uint32_t refr
                                        envoy::api::v2::core::ApiConfigSource& api_config_source) {
   // TODO(junr03): document the option to chose an api type once we have created
   // stronger constraints around v2.
-  if (api_type == ApiType::get().RestLegacy) {
-    api_config_source.set_api_type(envoy::api::v2::core::ApiConfigSource::REST_LEGACY);
-  } else if (api_type == ApiType::get().Rest) {
-    api_config_source.set_api_type(envoy::api::v2::core::ApiConfigSource::REST);
-  } else {
-    ASSERT(api_type == ApiType::get().Grpc);
+  if (api_type == ApiType::get().Grpc) {
     api_config_source.set_api_type(envoy::api::v2::core::ApiConfigSource::GRPC);
+    envoy::api::v2::core::GrpcService* grpc_service = api_config_source.add_grpc_services();
+    grpc_service->mutable_envoy_grpc()->set_cluster_name(cluster);
+  } else {
+    if (api_type == ApiType::get().RestLegacy) {
+      api_config_source.set_api_type(envoy::api::v2::core::ApiConfigSource::REST_LEGACY);
+    } else if (api_type == ApiType::get().Rest) {
+      api_config_source.set_api_type(envoy::api::v2::core::ApiConfigSource::REST);
+    }
+    api_config_source.add_cluster_names(cluster);
   }
-  api_config_source.add_cluster_names(cluster);
+
   api_config_source.mutable_refresh_delay()->CopyFrom(
       Protobuf::util::TimeUtil::MillisecondsToDuration(refresh_delay_ms));
 }
@@ -83,26 +87,21 @@ void Utility::checkApiConfigSourceNames(
   const bool is_grpc =
       (api_config_source.api_type() == envoy::api::v2::core::ApiConfigSource::GRPC);
 
-  if (api_config_source.cluster_names().size() == 0 &&
-      api_config_source.grpc_services().size() == 0) {
+  if (api_config_source.cluster_names().empty() && api_config_source.grpc_services().empty()) {
     throw EnvoyException("API configs must have either a gRPC service or a cluster name defined");
   }
 
   if (is_grpc) {
-    if (api_config_source.cluster_names().size() != 0) {
-      ENVOY_LOG_MISC(warn, "Setting a cluster name for API config source type "
-                           "envoy::api::v2::core::ConfigSource::GRPC is deprecated");
-    }
-    if (api_config_source.cluster_names().size() > 1) {
+    if (!api_config_source.cluster_names().empty()) {
       throw EnvoyException(
-          "envoy::api::v2::core::ConfigSource must have a singleton cluster name specified");
+          "envoy::api::v2::core::ConfigSource::GRPC must not have a cluster name specified.");
     }
     if (api_config_source.grpc_services().size() > 1) {
       throw EnvoyException(
           "envoy::api::v2::core::ConfigSource::GRPC must have a single gRPC service specified");
     }
   } else {
-    if (api_config_source.grpc_services().size() != 0) {
+    if (!api_config_source.grpc_services().empty()) {
       throw EnvoyException("envoy::api::v2::core::ConfigSource, if not of type gRPC, must not have "
                            "a gRPC service specified");
     }
@@ -219,11 +218,7 @@ Grpc::AsyncClientFactoryPtr Utility::factoryForGrpcApiConfigSource(
   Utility::checkApiConfigSourceNames(api_config_source);
 
   envoy::api::v2::core::GrpcService grpc_service;
-  if (api_config_source.cluster_names().empty()) {
-    grpc_service.MergeFrom(api_config_source.grpc_services(0));
-  } else {
-    grpc_service.mutable_envoy_grpc()->set_cluster_name(api_config_source.cluster_names(0));
-  }
+  grpc_service.MergeFrom(api_config_source.grpc_services(0));
 
   return async_client_manager.factoryForGrpcService(grpc_service, scope, false);
 }
diff --git a/test/common/config/utility_test.cc b/test/common/config/utility_test.cc
index d25fc023fba19..9e45d3df7e998 100644
--- a/test/common/config/utility_test.cc
+++ b/test/common/config/utility_test.cc
@@ -81,7 +81,8 @@ TEST(UtilityTest, TranslateApiConfigSource) {
                                     api_config_source_grpc);
   EXPECT_EQ(envoy::api::v2::core::ApiConfigSource::GRPC, api_config_source_grpc.api_type());
   EXPECT_EQ(30000, DurationUtil::durationToMilliseconds(api_config_source_grpc.refresh_delay()));
-  EXPECT_EQ("test_grpc_cluster", api_config_source_grpc.cluster_names(0));
+  EXPECT_EQ("test_grpc_cluster",
+            api_config_source_grpc.grpc_services(0).envoy_grpc().cluster_name());
 }
 
 TEST(UtilityTest, createTagProducer) {
@@ -216,8 +217,10 @@ TEST(UtilityTest, FactoryForGrpcApiConfigSource) {
     api_config_source.set_api_type(envoy::api::v2::core::ApiConfigSource::GRPC);
     api_config_source.add_cluster_names();
     // this also logs a warning for setting REST cluster names for a gRPC API config.
-    EXPECT_NO_THROW(
-        Utility::factoryForGrpcApiConfigSource(async_client_manager, api_config_source, scope));
+    EXPECT_THROW_WITH_REGEX(
+        Utility::factoryForGrpcApiConfigSource(async_client_manager, api_config_source, scope),
+        EnvoyException,
+        "envoy::api::v2::core::ConfigSource::GRPC must not have a cluster name specified.");
   }
 
   {
@@ -225,11 +228,10 @@ TEST(UtilityTest, FactoryForGrpcApiConfigSource) {
     api_config_source.set_api_type(envoy::api::v2::core::ApiConfigSource::GRPC);
     api_config_source.add_cluster_names();
     api_config_source.add_cluster_names();
-    // this also logs a warning for setting REST cluster names for a gRPC API config.
     EXPECT_THROW_WITH_REGEX(
         Utility::factoryForGrpcApiConfigSource(async_client_manager, api_config_source, scope),
         EnvoyException,
-        "envoy::api::v2::core::ConfigSource must have a singleton cluster name specified");
+        "envoy::api::v2::core::ConfigSource::GRPC must not have a cluster name specified.");
   }
 
   {
@@ -272,17 +274,14 @@ TEST(CheckApiConfigSourceSubscriptionBackingClusterTest, GrpcClusterTestAcrossTy
 
   // API of type GRPC
   api_config_source->set_api_type(envoy::api::v2::core::ApiConfigSource::GRPC);
-  api_config_source->add_cluster_names("foo_cluster");
 
   // GRPC cluster without GRPC services.
   EXPECT_THROW_WITH_MESSAGE(
       Utility::checkApiConfigSourceSubscriptionBackingCluster(cluster_map, *api_config_source),
-      EnvoyException,
-      "envoy::api::v2::core::ConfigSource must have a statically defined non-EDS cluster: "
-      "'foo_cluster' does not exist, was added via api, or is an EDS cluster");
+      EnvoyException, "API configs must have either a gRPC service or a cluster name defined");
 
   // Non-existent cluster.
-  api_config_source->add_grpc_services();
+  api_config_source->add_grpc_services()->mutable_envoy_grpc()->set_cluster_name("foo_cluster");
   EXPECT_THROW_WITH_MESSAGE(
       Utility::checkApiConfigSourceSubscriptionBackingCluster(cluster_map, *api_config_source),
       EnvoyException,
@@ -315,6 +314,13 @@ TEST(CheckApiConfigSourceSubscriptionBackingClusterTest, GrpcClusterTestAcrossTy
   EXPECT_CALL(*cluster.info_, addedViaApi());
   EXPECT_CALL(*cluster.info_, type());
   Utility::checkApiConfigSourceSubscriptionBackingCluster(cluster_map, *api_config_source);
+
+  // API with cluster_names set should be rejected.
+  api_config_source->add_cluster_names("foo_cluster");
+  EXPECT_THROW_WITH_MESSAGE(
+      Utility::checkApiConfigSourceSubscriptionBackingCluster(cluster_map, *api_config_source),
+      EnvoyException,
+      "envoy::api::v2::core::ConfigSource::GRPC must not have a cluster name specified.");
 }
 
 TEST(CheckApiConfigSourceSubscriptionBackingClusterTest, RestClusterTestAcrossTypes) {