diff --git a/test/unit_test/runtime/math_test.cpp b/test/unit_test/runtime/math_test.cpp
index 5c803c73..f03dc85c 100644
--- a/test/unit_test/runtime/math_test.cpp
+++ b/test/unit_test/runtime/math_test.cpp
@@ -65,10 +65,6 @@ TEST_CASE("'cbrt()' on quantity changes the value and the dimension accordingly"
 TEST_CASE("'fma()' on quantity changes the value and the dimension accordingly", "[math][fma]")
 {
   REQUIRE(fma(1.0 * isq::length[m], 2.0 * one, 2.0 * isq::length[m]) == 4.0 * isq::length[m]);
-}
-
-TEST_CASE("'fma()' returns a common reference.", "[math][fma]")
-{
   REQUIRE(fma(isq::speed(10.0 * m / s), isq::time(2.0 * s), isq::height(42.0 * m)) == isq::length(62.0 * m));
 }
 
diff --git a/test/unit_test/static/math_test.cpp b/test/unit_test/static/math_test.cpp
index 84848c02..528ea206 100644
--- a/test/unit_test/static/math_test.cpp
+++ b/test/unit_test/static/math_test.cpp
@@ -40,10 +40,19 @@ template<typename T1, typename T2, typename... Ts>
 
 #if __cpp_lib_constexpr_cmath || MP_UNITS_COMP_GCC
 
+template<auto One>
+concept invalid_fma = requires {
+  requires !requires { fma(2 * m, One, 2 * s); };
+  requires !requires { fma(2 * m, One, 2 * cm); };
+};
+static_assert(invalid_fma<1 * one>);
+
+
 static_assert(compare(fma(2.0 * s, 3.0 * Hz, 1.0 * one), 7.0 * one));
 static_assert(compare(fma(2.0 * one, 3.0 * m, 1.0 * m), 7.0 * m));
 static_assert(compare(fma(2.0 * m, 3.0 * one, 1.0 * m), 7.0 * m));
 static_assert(compare(fma(2 * m, 3.0f * m, 1.0 * m2), 7.0 * m2));
+static_assert(compare(fma(isq::width(2.0 * m), 2.0 * one, isq::height(3.0 * m)), isq::length(7.0 * m)));
 static_assert(compare(pow<0>(2 * m), 1 * one));
 static_assert(compare(pow<1>(2 * m), 2 * m));
 static_assert(compare(pow<2>(2 * m), 4 * pow<2>(m), 4 * m2));