diff --git a/Source/Core/Core/HW/SI/SI_DeviceGBA.h b/Source/Core/Core/HW/SI/SI_DeviceGBA.h
index 73ea2418f7..2351639e67 100644
--- a/Source/Core/Core/HW/SI/SI_DeviceGBA.h
+++ b/Source/Core/Core/HW/SI/SI_DeviceGBA.h
@@ -21,7 +21,7 @@ void GBAConnectionWaiter_Shutdown();
 class GBASockServer
 {
 public:
-  GBASockServer(int _iDeviceNumber);
+  explicit GBASockServer(int _iDeviceNumber);
   ~GBASockServer();
 
   void Disconnect();