diff --git a/FirebaseCore/Internal/Sources/HeartbeatLogging/HeartbeatController.swift b/FirebaseCore/Internal/Sources/HeartbeatLogging/HeartbeatController.swift
index e4a2cc4c335..e7f4ece2781 100644
--- a/FirebaseCore/Internal/Sources/HeartbeatLogging/HeartbeatController.swift
+++ b/FirebaseCore/Internal/Sources/HeartbeatLogging/HeartbeatController.swift
@@ -126,34 +126,30 @@ public final class HeartbeatController {
     }
   }
 
-  @available(iOS 13.0, macOS 10.15, macCatalyst 13.0, tvOS 13.0, watchOS 6.0, *)
-  public func flushAsync() async -> HeartbeatsPayload {
-    return await withCheckedContinuation { continuation in
-      let resetTransform = { (heartbeatsBundle: HeartbeatsBundle?) -> HeartbeatsBundle? in
-        guard let oldHeartbeatsBundle = heartbeatsBundle else {
-          return nil // Storage was empty.
-        }
-        // The new value that's stored will use the old's cache to prevent the
-        // logging of duplicates after flushing.
-        return HeartbeatsBundle(
-          capacity: self.heartbeatsStorageCapacity,
-          cache: oldHeartbeatsBundle.lastAddedHeartbeatDates
-        )
+  public func flushAsync(completionHandler: @escaping (HeartbeatsPayload) -> Void) {
+    let resetTransform = { (heartbeatsBundle: HeartbeatsBundle?) -> HeartbeatsBundle? in
+      guard let oldHeartbeatsBundle = heartbeatsBundle else {
+        return nil // Storage was empty.
       }
+      // The new value that's stored will use the old's cache to prevent the
+      // logging of duplicates after flushing.
+      return HeartbeatsBundle(
+        capacity: self.heartbeatsStorageCapacity,
+        cache: oldHeartbeatsBundle.lastAddedHeartbeatDates
+      )
+    }
 
-      // Asynchronously gets and returns the stored heartbeats, resetting storage
-      // using the given transform.
-      storage.getAndSetAsync(using: resetTransform) { result in
-        switch result {
-        case let .success(heartbeatsBundle):
-          // If no heartbeats bundle was stored, return an empty payload.
-          continuation
-            .resume(returning: heartbeatsBundle?.makeHeartbeatsPayload() ?? HeartbeatsPayload
-              .emptyPayload)
-        case .failure:
-          // If the operation throws, assume no heartbeat(s) were retrieved or set.
-          continuation.resume(returning: HeartbeatsPayload.emptyPayload)
-        }
+    // Asynchronously gets and returns the stored heartbeats, resetting storage
+    // using the given transform.
+    storage.getAndSetAsync(using: resetTransform) { result in
+      switch result {
+      case let .success(heartbeatsBundle):
+        // If no heartbeats bundle was stored, return an empty payload.
+        completionHandler(heartbeatsBundle?.makeHeartbeatsPayload() ?? HeartbeatsPayload
+          .emptyPayload)
+      case .failure:
+        // If the operation throws, assume no heartbeat(s) were retrieved or set.
+        completionHandler(HeartbeatsPayload.emptyPayload)
       }
     }
   }
diff --git a/FirebaseCore/Internal/Sources/HeartbeatLogging/_ObjC_HeartbeatController.swift b/FirebaseCore/Internal/Sources/HeartbeatLogging/_ObjC_HeartbeatController.swift
index cef5c7d9a8e..c60a1e11cc5 100644
--- a/FirebaseCore/Internal/Sources/HeartbeatLogging/_ObjC_HeartbeatController.swift
+++ b/FirebaseCore/Internal/Sources/HeartbeatLogging/_ObjC_HeartbeatController.swift
@@ -52,15 +52,8 @@ public class _ObjC_HeartbeatController: NSObject {
   public func flushAsync(completionHandler: @escaping (_ObjC_HeartbeatsPayload) -> Void) {
     // TODO: When minimum version moves to iOS 13.0, restore the async version
     // removed in #13952.
-    if #available(iOS 13.0, macOS 10.15, macCatalyst 13.0, tvOS 13.0, watchOS 6.0, *) {
-      Task {
-        let heartbeatsPayload = await heartbeatController.flushAsync()
-        completionHandler(_ObjC_HeartbeatsPayload(heartbeatsPayload))
-      }
-    } else {
-      // It is not expected to reach this state as this API should only be
-      // called on iOS 13.0+.
-      completionHandler(_ObjC_HeartbeatsPayload(HeartbeatsPayload.emptyPayload))
+    heartbeatController.flushAsync { heartbeatsPayload in
+      completionHandler(_ObjC_HeartbeatsPayload(heartbeatsPayload))
     }
   }
 
diff --git a/FirebaseCore/Internal/Tests/Integration/HeartbeatLoggingIntegrationTests.swift b/FirebaseCore/Internal/Tests/Integration/HeartbeatLoggingIntegrationTests.swift
index b306405f4bd..3a9823aa94a 100644
--- a/FirebaseCore/Internal/Tests/Integration/HeartbeatLoggingIntegrationTests.swift
+++ b/FirebaseCore/Internal/Tests/Integration/HeartbeatLoggingIntegrationTests.swift
@@ -52,29 +52,36 @@ class HeartbeatLoggingIntegrationTests: XCTestCase {
     )
   }
 
-  @available(iOS 13.0, macOS 10.15, macCatalyst 13.0, tvOS 13.0, watchOS 6.0, *)
-  func testLogAndFlushAsync() async throws {
+  func testLogAndFlushAsync() throws {
     // Given
     let heartbeatController = HeartbeatController(id: #function)
     let expectedDate = HeartbeatsPayload.dateFormatter.string(from: Date())
+    let expectation = self.expectation(description: #function)
     // When
     heartbeatController.log("dummy_agent")
-    let payload = await heartbeatController.flushAsync()
-    // Then
-    try HeartbeatLoggingTestUtils.assertEqualPayloadStrings(
-      payload.headerValue(),
-      """
-      {
-        "version": 2,
-        "heartbeats": [
+    heartbeatController.flushAsync { payload in
+      // Then
+      do {
+        try HeartbeatLoggingTestUtils.assertEqualPayloadStrings(
+          payload.headerValue(),
+          """
           {
-            "agent": "dummy_agent",
-            "dates": ["\(expectedDate)"]
+            "version": 2,
+            "heartbeats": [
+              {
+                "agent": "dummy_agent",
+                "dates": ["\(expectedDate)"]
+              }
+            ]
           }
-        ]
+          """
+        )
+        expectation.fulfill()
+      } catch {
+        XCTFail("Unexpected error: \(error)")
       }
-      """
-    )
+    }
+    waitForExpectations(timeout: 1.0)
   }
 
   /// This test may flake if it is executed during the transition from one day to the next.
diff --git a/FirebaseCore/Internal/Tests/Unit/HeartbeatControllerTests.swift b/FirebaseCore/Internal/Tests/Unit/HeartbeatControllerTests.swift
index ddf3d1c5d9d..82691ed3f24 100644
--- a/FirebaseCore/Internal/Tests/Unit/HeartbeatControllerTests.swift
+++ b/FirebaseCore/Internal/Tests/Unit/HeartbeatControllerTests.swift
@@ -58,35 +58,41 @@ class HeartbeatControllerTests: XCTestCase {
     assertHeartbeatControllerFlushesEmptyPayload(controller)
   }
 
-  @available(iOS 13.0, macOS 10.15, macCatalyst 13.0, tvOS 13.0, watchOS 6.0, *)
-  func testLogAndFlushAsync() async throws {
+  func testLogAndFlushAsync() throws {
     // Given
     let controller = HeartbeatController(
       storage: HeartbeatStorageFake(),
       dateProvider: { self.date }
     )
+    let expectation = expectation(description: #function)
 
     assertHeartbeatControllerFlushesEmptyPayload(controller)
 
     // When
     controller.log("dummy_agent")
-    let heartbeatPayload = await controller.flushAsync()
-
-    // Then
-    try HeartbeatLoggingTestUtils.assertEqualPayloadStrings(
-      heartbeatPayload.headerValue(),
-      """
-      {
-        "version": 2,
-        "heartbeats": [
+    controller.flushAsync { heartbeatPayload in
+      // Then
+      do {
+        try HeartbeatLoggingTestUtils.assertEqualPayloadStrings(
+          heartbeatPayload.headerValue(),
+          """
           {
-            "agent": "dummy_agent",
-            "dates": ["2021-11-01"]
+            "version": 2,
+            "heartbeats": [
+              {
+                "agent": "dummy_agent",
+                "dates": ["2021-11-01"]
+              }
+            ]
           }
-        ]
+          """
+        )
+        expectation.fulfill()
+      } catch {
+        XCTFail("Unexpected error: \(error)")
       }
-      """
-    )
+    }
+    waitForExpectations(timeout: 1.0)
 
     assertHeartbeatControllerFlushesEmptyPayload(controller)
   }