diff --git a/tests/numeric-test.vala b/tests/numeric-test.vala
index aa8b524..a6bba69 100644
--- a/tests/numeric-test.vala
+++ b/tests/numeric-test.vala
@@ -39,6 +39,8 @@ public int main (string[] args)
 
 	Test.add_func ("/float128", () => {
 		float128 f = 12.5;
+		float128 g = 13.5;
+		assert (26 == (double) (f + g));
 		assert (12.5 == (double) f);
 		assert ("1.096910e+00" == Numeric.Math.log10q (f).to_string ("%Qe"));
 		assert ("1.189731e+4932" == float128.MAX.to_string ("%Qe"));