diff --git a/include/mtl/tests/vec.hpp b/include/mtl/tests/vec.hpp
index 0d50a27..88ed9c4 100644
--- a/include/mtl/tests/vec.hpp
+++ b/include/mtl/tests/vec.hpp
@@ -39,6 +39,8 @@ public:
 		add_test(&transpose_v2, "transpose_v2");
 		add_test(&transpose_v3, "transpose_v3");
 		add_test(&transpose_v4, "transpose_v4");
+
+		add_test(&projection_v4, "projection_v4");
 	}
 
 	virtual string_view name() {
@@ -92,6 +94,8 @@ public:
 	GBA_IWRAM ARM_MODE static bool transpose_v2();
 	GBA_IWRAM ARM_MODE static bool transpose_v3();
 	GBA_IWRAM ARM_MODE static bool transpose_v4();
+
+	GBA_IWRAM ARM_MODE static bool projection_v4();
 };
 
 } // namespace test
diff --git a/src/tests/vec.cpp b/src/tests/vec.cpp
index 05b1413..5efeac5 100644
--- a/src/tests/vec.cpp
+++ b/src/tests/vec.cpp
@@ -342,6 +342,31 @@ bool vec_suite::transpose_v4() {
 	return true;
 }
 
+bool vec_suite::projection_v4() {
+	struct {
+		NOINLINE GBA_IWRAM ARM_MODE
+		vec4 operator()(vec4 a, vec4 b) {
+			start_timer();
+			vec4 r = b * (a * b) / b.magnitude_sqr();
+			end_timer();
+			return r;
+		}
+	} f;
+
+	vec4 a(8, 3, 7, 0);
+	vec4 b(-3, 4, 14, 0);
+
+	vec4 c = f(a, b);
+	
+	vec4 exp(fixed::from_raw(-74), fixed::from_raw(99), fixed::from_raw(348), 0);
+
+	log::debug << "A = " << a << endl;
+	log::debug << "B = " << b << endl;
+	log::debug << "C = proj(A, B) = " << c << endl;
+
+	return c == exp;
+}
+
 } // namespace test
 
 } // namespace mtl