diff --git a/Sources/DataConnect.swift b/Sources/DataConnect.swift
index 8fa0e69..4688380 100644
--- a/Sources/DataConnect.swift
+++ b/Sources/DataConnect.swift
@@ -24,7 +24,7 @@ public class DataConnect {
   private var app: FirebaseApp
   private var settings: DataConnectSettings
 
-  private var grpcClient: GrpcClient
+  private(set) var grpcClient: GrpcClient
   private var operationsManager: OperationsManager
 
   private static var instanceStore = InstanceStore()
@@ -57,12 +57,12 @@ public class DataConnect {
     // self.grpcClient.close
     // self.operations.close
 
-    guard let projectID = app.options.projectID else {
+    guard app.options.projectID != nil else {
       fatalError("Firebase DataConnect requires the projectID to be set in the app options")
     }
 
     grpcClient = GrpcClient(
-      projectId: projectID,
+      app: app,
       settings: settings,
       connectorConfig: connectorConfig,
       auth: Auth.auth(app: app),
@@ -79,12 +79,12 @@ public class DataConnect {
     self.settings = settings
     self.connectorConfig = connectorConfig
 
-    guard let projectID = app.options.projectID else {
+    guard app.options.projectID != nil else {
       fatalError("Firebase DataConnect requires the projectID to be set in the app options")
     }
 
     grpcClient = GrpcClient(
-      projectId: projectID,
+      app: self.app,
       settings: settings,
       connectorConfig: connectorConfig,
       auth: Auth.auth(app: app),
diff --git a/Sources/Internal/GrpcClient.swift b/Sources/Internal/GrpcClient.swift
index c8829c4..fe37b7a 100644
--- a/Sources/Internal/GrpcClient.swift
+++ b/Sources/Internal/GrpcClient.swift
@@ -16,7 +16,7 @@ import Foundation
 
 import FirebaseAppCheck
 import FirebaseAuth
-import FirebaseCoreInternal
+import FirebaseCore
 import GRPC
 import NIOCore
 import NIOHPACK
@@ -28,6 +28,8 @@ import SwiftProtobuf
 actor GrpcClient: CustomStringConvertible {
   nonisolated let description: String
 
+  private let app: FirebaseApp
+
   private let projectId: String
 
   private let threadPoolSize = 1
@@ -42,10 +44,11 @@ actor GrpcClient: CustomStringConvertible {
 
   private let appCheck: AppCheck?
 
-  private enum RequestHeaders {
+  enum RequestHeaders {
     static let googRequestParamsHeader = "x-goog-request-params"
     static let authorizationHeader = "x-firebase-auth-token"
     static let appCheckHeader = "X-Firebase-AppCheck"
+    static let firebaseAppId = "x-firebase-gmpid"
   }
 
   private let googRequestHeaderValue: String
@@ -69,10 +72,16 @@ actor GrpcClient: CustomStringConvertible {
     }
   }()
 
-  init(projectId: String, settings: DataConnectSettings, connectorConfig: ConnectorConfig,
+  init(app: FirebaseApp, settings: DataConnectSettings, connectorConfig: ConnectorConfig,
        auth: Auth,
        appCheck: AppCheck?) {
+    self.app = app
+
+    guard let projectId = app.options.projectID else {
+      fatalError("Data Connect requires a Firebase project ID to be specified.")
+    }
     self.projectId = projectId
+
     serverSettings = settings
     self.connectorConfig = connectorConfig
     self.auth = auth
@@ -173,10 +182,11 @@ actor GrpcClient: CustomStringConvertible {
     }
   }
 
-  private func createCallOptions() async -> CallOptions {
+  func createCallOptions() async -> CallOptions {
     var headers = HPACKHeaders()
 
     headers.add(name: RequestHeaders.googRequestParamsHeader, value: googRequestHeaderValue)
+    headers.add(name: RequestHeaders.firebaseAppId, value: app.options.googleAppID)
 
     // Add Auth token if available
     do {
diff --git a/Tests/Unit/HeaderTests.swift b/Tests/Unit/HeaderTests.swift
new file mode 100644
index 0000000..68207f1
--- /dev/null
+++ b/Tests/Unit/HeaderTests.swift
@@ -0,0 +1,53 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import FirebaseCore
+@testable import FirebaseDataConnect
+import Foundation
+import GRPC
+
+import XCTest
+
+final class HeaderTests: XCTestCase {
+  static var defaultApp: FirebaseApp?
+
+  static var options: FirebaseOptions = {
+    let options = FirebaseOptions(googleAppID: "0:0000000000000:ios:testAppId",
+                                  gcmSenderID: "00000000000000000-00000000000-000000000")
+    options.projectID = "fdc-test"
+    options.apiKey = "testDummyApiKey"
+    return options
+  }()
+
+  var fakeConnectorConfigOne = ConnectorConfig(
+    serviceId: "dataconnect",
+    location: "us-central1",
+    connector: "kitchensink"
+  )
+
+  override class func setUp() {
+    FirebaseApp.configure(options: options)
+    defaultApp = FirebaseApp.app()
+  }
+
+  func testGmpAppIdHeader() async throws {
+    let dcOne = DataConnect.dataConnect(connectorConfig: fakeConnectorConfigOne)
+    let callOptions = await dcOne.grpcClient.createCallOptions()
+    let values = callOptions.customMetadata.values(
+      forHeader: GrpcClient.RequestHeaders.firebaseAppId, canonicalForm: false
+    )
+    let contains = values.contains { $0 == HeaderTests.defaultApp!.options.googleAppID }
+    XCTAssertTrue(contains)
+  }
+}