diff --git a/Source/Core/Core/HW/SI/SI_Device.cpp b/Source/Core/Core/HW/SI/SI_Device.cpp
index 03ee5836f4..da18ac595c 100644
--- a/Source/Core/Core/HW/SI/SI_Device.cpp
+++ b/Source/Core/Core/HW/SI/SI_Device.cpp
@@ -18,6 +18,23 @@
 #include "Core/HW/SI/SI_DeviceKeyboard.h"
 #include "Core/HW/SI/SI_DeviceNull.h"
 
+ISIDevice::ISIDevice(SIDevices device_type, int device_number)
+    : m_device_number(device_number), m_device_type(device_type)
+{
+}
+
+ISIDevice::~ISIDevice() = default;
+
+int ISIDevice::GetDeviceNumber() const
+{
+  return m_device_number;
+}
+
+SIDevices ISIDevice::GetDeviceType() const
+{
+  return m_device_type;
+}
+
 int ISIDevice::RunBuffer(u8* buffer, int length)
 {
 #ifdef _DEBUG
@@ -48,6 +65,10 @@ int ISIDevice::TransferInterval()
   return 0;
 }
 
+void ISIDevice::DoState(PointerWrap& p)
+{
+}
+
 // Check if a device class is inheriting from CSIDevice_GCController
 // The goal of this function is to avoid special casing a long list of
 // device types when there is no "real" input device, e.g. when playing
diff --git a/Source/Core/Core/HW/SI/SI_Device.h b/Source/Core/Core/HW/SI/SI_Device.h
index 388892bfe0..6702c33969 100644
--- a/Source/Core/Core/HW/SI/SI_Device.h
+++ b/Source/Core/Core/HW/SI/SI_Device.h
@@ -73,14 +73,12 @@ enum SIDevices : int
 class ISIDevice
 {
 public:
-  // Constructor
-  ISIDevice(SIDevices device_type, int device_number)
-      : m_device_number(device_number), m_device_type(device_type)
-  {
-  }
+  ISIDevice(SIDevices device_type, int device_number);
+  virtual ~ISIDevice();
+
+  int GetDeviceNumber() const;
+  SIDevices GetDeviceType() const;
 
-  // Destructor
-  virtual ~ISIDevice() {}
   // Run the SI Buffer
   virtual int RunBuffer(u8* buffer, int length);
   virtual int TransferInterval();
@@ -92,9 +90,7 @@ public:
   virtual void SendCommand(u32 command, u8 poll) = 0;
 
   // Savestate support
-  virtual void DoState(PointerWrap& p) {}
-  int GetDeviceNumber() const { return m_device_number; }
-  SIDevices GetDeviceType() const { return m_device_type; }
+  virtual void DoState(PointerWrap& p);
 
 protected:
   int m_device_number;