diff --git a/Source/Core/Common/x64Emitter.h b/Source/Core/Common/x64Emitter.h
index 6916883d8969..57bfc73d4fa3 100644
--- a/Source/Core/Common/x64Emitter.h
+++ b/Source/Core/Common/x64Emitter.h
@@ -342,7 +342,7 @@ class XEmitter
   void CheckFlags();
 
   void Rex(int w, int r, int x, int b);
-  void WriteModRM(int mod, int rm, int reg);
+  void WriteModRM(int mod, int reg, int rm);
   void WriteSIB(int scale, int index, int base);
   void WriteSimple1Byte(int bits, u8 byte, X64Reg reg);
   void WriteSimple2Byte(int bits, u8 byte1, u8 byte2, X64Reg reg);