diff --git a/test/integration/fake_upstream.cc b/test/integration/fake_upstream.cc
index c942e387ce5d..e35bb07a1183 100644
--- a/test/integration/fake_upstream.cc
+++ b/test/integration/fake_upstream.cc
@@ -410,8 +410,10 @@ std::string FakeRawConnection::waitForData(uint64_t num_bytes) {
 }
 
 void FakeRawConnection::write(const std::string& data, bool end_stream) {
+  std::unique_lock<std::mutex> lock(lock_);
   ASSERT_FALSE(disconnected_);
   connection_.dispatcher().post([data, end_stream, this]() -> void {
+    std::unique_lock<std::mutex> lock(lock_);
     ASSERT_FALSE(disconnected_);
     Buffer::OwnedImpl to_write(data);
     connection_.write(to_write, end_stream);
diff --git a/test/integration/fake_upstream.h b/test/integration/fake_upstream.h
index f7af85e61574..d38b2df66522 100644
--- a/test/integration/fake_upstream.h
+++ b/test/integration/fake_upstream.h
@@ -197,7 +197,10 @@ class FakeConnectionBase : public Network::ConnectionCallbacks {
     connection_.dispatcher().post([this]() -> void { connection_.addConnectionCallbacks(*this); });
   }
   void enableHalfClose(bool enabled);
-  bool connected() const { return !disconnected_; }
+  bool connected() const {
+    std::unique_lock<std::mutex> lock(lock_);
+    return !disconnected_;
+  }
 
 protected:
   FakeConnectionBase(QueuedConnectionWrapperPtr connection_wrapper)
@@ -205,7 +208,7 @@ class FakeConnectionBase : public Network::ConnectionCallbacks {
         connection_wrapper_(std::move(connection_wrapper)) {}
 
   Network::Connection& connection_;
-  std::mutex lock_;
+  mutable std::mutex lock_;
   std::condition_variable connection_event_;
   bool disconnected_{};
   bool half_closed_{};