diff --git a/usb/1.0/default/Usb.h b/usb/1.0/default/Usb.h
index cf418f4..c34d080 100644
--- a/usb/1.0/default/Usb.h
+++ b/usb/1.0/default/Usb.h
@@ -32,6 +32,7 @@
 using ::android::sp;
 
 struct Usb : public IUsb {
+    Usb();
     Return<void> switchRole(const hidl_string& portName, const PortRole& role) override;
     Return<void> setCallback(const sp<IUsbCallback>& callback) override;
     Return<void> queryPortStatus() override;
@@ -39,6 +40,7 @@
     sp<IUsbCallback> mCallback;
     private:
         pthread_t mPoll;
+        pthread_mutex_t mLock = PTHREAD_MUTEX_INITIALIZER;
 };
 
 }  // namespace implementation