diff --git a/atrace/1.0/default/AtraceDevice.h b/atrace/1.0/default/AtraceDevice.h
index e700f89..ab87c65 100644
--- a/atrace/1.0/default/AtraceDevice.h
+++ b/atrace/1.0/default/AtraceDevice.h
@@ -36,12 +36,16 @@
 using ::android::hardware::Void;
 
 struct AtraceDevice : public IAtraceDevice {
+    AtraceDevice();
     // Methods from ::android::hardware::atrace::V1_0::IAtraceDevice follow.
     Return<void> listCategories(listCategories_cb _hidl_cb) override;
     Return<::android::hardware::atrace::V1_0::Status> enableCategories(
         const hidl_vec<hidl_string>& categories) override;
     Return<::android::hardware::atrace::V1_0::Status> disableAllCategories() override;
 
+  private:
+    std::string tracefs_event_root_;
+
     // Methods from ::android::hidl::base::V1_0::IBase follow.
 };