diff --git a/math/int_test.go b/math/int_test.go
index 4da1cae423..f6c476410f 100644
--- a/math/int_test.go
+++ b/math/int_test.go
@@ -546,6 +546,7 @@ var sizeTests = []struct {
 	{"9999999999999", 13},
 	{"99999999999999", 14},
 	{"999999999999999", 15},
+	{"1000000000000000", 16},
 	{"9999999999999999", 16},
 	{"99999999999999999", 17},
 	{"999999999999999999", 18},