diff --git a/src/v3/agents_client.ts b/src/v3/agents_client.ts
index 21ce19de..40348166 100644
--- a/src/v3/agents_client.ts
+++ b/src/v3/agents_client.ts
@@ -142,6 +142,8 @@ export class AgentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/entity_types_client.ts b/src/v3/entity_types_client.ts
index 5c3ec66b..fac87534 100644
--- a/src/v3/entity_types_client.ts
+++ b/src/v3/entity_types_client.ts
@@ -140,6 +140,8 @@ export class EntityTypesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/environments_client.ts b/src/v3/environments_client.ts
index 05201382..eb95c3e8 100644
--- a/src/v3/environments_client.ts
+++ b/src/v3/environments_client.ts
@@ -142,6 +142,8 @@ export class EnvironmentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/experiments_client.ts b/src/v3/experiments_client.ts
index c2cdbfbf..f93b7675 100644
--- a/src/v3/experiments_client.ts
+++ b/src/v3/experiments_client.ts
@@ -140,6 +140,8 @@ export class ExperimentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/flows_client.ts b/src/v3/flows_client.ts
index 671c9912..e5313cbf 100644
--- a/src/v3/flows_client.ts
+++ b/src/v3/flows_client.ts
@@ -142,6 +142,8 @@ export class FlowsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/intents_client.ts b/src/v3/intents_client.ts
index f0f6b6eb..380c2005 100644
--- a/src/v3/intents_client.ts
+++ b/src/v3/intents_client.ts
@@ -140,6 +140,8 @@ export class IntentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/pages_client.ts b/src/v3/pages_client.ts
index d84e96fb..7b9032f3 100644
--- a/src/v3/pages_client.ts
+++ b/src/v3/pages_client.ts
@@ -140,6 +140,8 @@ export class PagesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/security_settings_service_client.ts b/src/v3/security_settings_service_client.ts
index 4cca3fff..9d525ac7 100644
--- a/src/v3/security_settings_service_client.ts
+++ b/src/v3/security_settings_service_client.ts
@@ -141,6 +141,8 @@ export class SecuritySettingsServiceClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/session_entity_types_client.ts b/src/v3/session_entity_types_client.ts
index e5d4c108..5974182d 100644
--- a/src/v3/session_entity_types_client.ts
+++ b/src/v3/session_entity_types_client.ts
@@ -140,6 +140,8 @@ export class SessionEntityTypesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/sessions_client.ts b/src/v3/sessions_client.ts
index 1ed8dda0..197378d0 100644
--- a/src/v3/sessions_client.ts
+++ b/src/v3/sessions_client.ts
@@ -133,6 +133,8 @@ export class SessionsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/test_cases_client.ts b/src/v3/test_cases_client.ts
index cac2431c..3c8ab51e 100644
--- a/src/v3/test_cases_client.ts
+++ b/src/v3/test_cases_client.ts
@@ -143,6 +143,8 @@ export class TestCasesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/transition_route_groups_client.ts b/src/v3/transition_route_groups_client.ts
index e3182209..fc5f04b3 100644
--- a/src/v3/transition_route_groups_client.ts
+++ b/src/v3/transition_route_groups_client.ts
@@ -141,6 +141,8 @@ export class TransitionRouteGroupsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/versions_client.ts b/src/v3/versions_client.ts
index 477a8ed2..921f861b 100644
--- a/src/v3/versions_client.ts
+++ b/src/v3/versions_client.ts
@@ -142,6 +142,8 @@ export class VersionsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3/webhooks_client.ts b/src/v3/webhooks_client.ts
index d0cec2c9..be108898 100644
--- a/src/v3/webhooks_client.ts
+++ b/src/v3/webhooks_client.ts
@@ -140,6 +140,8 @@ export class WebhooksClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/agents_client.ts b/src/v3beta1/agents_client.ts
index 2f1bc40a..db84910c 100644
--- a/src/v3beta1/agents_client.ts
+++ b/src/v3beta1/agents_client.ts
@@ -142,6 +142,8 @@ export class AgentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/entity_types_client.ts b/src/v3beta1/entity_types_client.ts
index 619b5073..10a63dd1 100644
--- a/src/v3beta1/entity_types_client.ts
+++ b/src/v3beta1/entity_types_client.ts
@@ -140,6 +140,8 @@ export class EntityTypesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/environments_client.ts b/src/v3beta1/environments_client.ts
index a42f73b0..d1bbee1c 100644
--- a/src/v3beta1/environments_client.ts
+++ b/src/v3beta1/environments_client.ts
@@ -142,6 +142,8 @@ export class EnvironmentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/experiments_client.ts b/src/v3beta1/experiments_client.ts
index 69b3d164..c14469fc 100644
--- a/src/v3beta1/experiments_client.ts
+++ b/src/v3beta1/experiments_client.ts
@@ -140,6 +140,8 @@ export class ExperimentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/flows_client.ts b/src/v3beta1/flows_client.ts
index ac772e2e..56452200 100644
--- a/src/v3beta1/flows_client.ts
+++ b/src/v3beta1/flows_client.ts
@@ -142,6 +142,8 @@ export class FlowsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/intents_client.ts b/src/v3beta1/intents_client.ts
index e6725f61..0b7906f7 100644
--- a/src/v3beta1/intents_client.ts
+++ b/src/v3beta1/intents_client.ts
@@ -140,6 +140,8 @@ export class IntentsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/pages_client.ts b/src/v3beta1/pages_client.ts
index 4d2f2b24..b9283b1c 100644
--- a/src/v3beta1/pages_client.ts
+++ b/src/v3beta1/pages_client.ts
@@ -140,6 +140,8 @@ export class PagesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/security_settings_service_client.ts b/src/v3beta1/security_settings_service_client.ts
index 2b18833e..f87c431d 100644
--- a/src/v3beta1/security_settings_service_client.ts
+++ b/src/v3beta1/security_settings_service_client.ts
@@ -141,6 +141,8 @@ export class SecuritySettingsServiceClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/session_entity_types_client.ts b/src/v3beta1/session_entity_types_client.ts
index 93fe6e8a..d969338d 100644
--- a/src/v3beta1/session_entity_types_client.ts
+++ b/src/v3beta1/session_entity_types_client.ts
@@ -140,6 +140,8 @@ export class SessionEntityTypesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/sessions_client.ts b/src/v3beta1/sessions_client.ts
index eda4c927..b70a5b67 100644
--- a/src/v3beta1/sessions_client.ts
+++ b/src/v3beta1/sessions_client.ts
@@ -133,6 +133,8 @@ export class SessionsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/test_cases_client.ts b/src/v3beta1/test_cases_client.ts
index cc0b04c8..5e45a718 100644
--- a/src/v3beta1/test_cases_client.ts
+++ b/src/v3beta1/test_cases_client.ts
@@ -143,6 +143,8 @@ export class TestCasesClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/transition_route_groups_client.ts b/src/v3beta1/transition_route_groups_client.ts
index 553fefb3..3cc3045c 100644
--- a/src/v3beta1/transition_route_groups_client.ts
+++ b/src/v3beta1/transition_route_groups_client.ts
@@ -141,6 +141,8 @@ export class TransitionRouteGroupsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/versions_client.ts b/src/v3beta1/versions_client.ts
index c1c6127e..9d2981e5 100644
--- a/src/v3beta1/versions_client.ts
+++ b/src/v3beta1/versions_client.ts
@@ -142,6 +142,8 @@ export class VersionsClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);
diff --git a/src/v3beta1/webhooks_client.ts b/src/v3beta1/webhooks_client.ts
index af570a61..4348464a 100644
--- a/src/v3beta1/webhooks_client.ts
+++ b/src/v3beta1/webhooks_client.ts
@@ -140,6 +140,8 @@ export class WebhooksClient {
     }
     if (!opts.fallback) {
       clientHeader.push(`grpc/${this._gaxGrpc.grpcVersion}`);
+    } else if (opts.fallback === 'rest') {
+      clientHeader.push(`rest/${this._gaxGrpc.grpcVersion}`);
     }
     if (opts.libName && opts.libVersion) {
       clientHeader.push(`${opts.libName}/${opts.libVersion}`);