diff --git a/dev/CMakeLists.txt b/dev/CMakeLists.txt
index 4895ce0..61704c9 100644
--- a/dev/CMakeLists.txt
+++ b/dev/CMakeLists.txt
@@ -45,7 +45,8 @@ else()
 endif()
 
 add_custom_target(CopyHeader
-    COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_BINARY_DIR}/olcPixelGameEngine3.h ${REPO_ROOT_DIR}/olcPixelGameEngine3.h
+    BYPRODUCTS ${REPO_ROOT_DIR}/olcPixelGameEngine3.h
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different ${CMAKE_BINARY_DIR}/olcPixelGameEngine3.h ${REPO_ROOT_DIR}/olcPixelGameEngine3.h
     DEPENDS olcPixelGameEngine3.h
 )
 
diff --git a/dev/src/vector4d.h b/dev/src/vector4d.h
index 3661b50..2b477b7 100644
--- a/dev/src/vector4d.h
+++ b/dev/src/vector4d.h
@@ -310,6 +310,13 @@ namespace olc
 		return lhs;
 	}
 
+	template<class TL, class TR>
+	inline constexpr auto operator -= (v_4d<TL>& lhs, const v_4d<TR>& rhs)
+	{
+		lhs = lhs - rhs;
+		return lhs;
+	}
+
 	// Greater/Less-Than Operator overloads - mathematically useless, but handy for "sorted" container storage
 	template<class TL, class TR>
 	inline constexpr bool operator < (const v_4d<TL>& lhs, const v_4d<TR>& rhs)
diff --git a/olcPixelGameEngine3.h b/olcPixelGameEngine3.h
index 2b919d7..c610efb 100644
--- a/olcPixelGameEngine3.h
+++ b/olcPixelGameEngine3.h
@@ -1309,6 +1309,13 @@ namespace olc
 		return lhs;
 	}
 
+	template<class TL, class TR>
+	inline constexpr auto operator -= (v_4d<TL>& lhs, const v_4d<TR>& rhs)
+	{
+		lhs = lhs - rhs;
+		return lhs;
+	}
+
 	// Greater/Less-Than Operator overloads - mathematically useless, but handy for "sorted" container storage
 	template<class TL, class TR>
 	inline constexpr bool operator < (const v_4d<TL>& lhs, const v_4d<TR>& rhs)