diff --git a/src/math/big/int_test.go b/src/math/big/int_test.go
index 88c8c2bb641..97874626f33 100644
--- a/src/math/big/int_test.go
+++ b/src/math/big/int_test.go
@@ -387,6 +387,11 @@ func TestSetBytes(t *testing.T) {
 }
 
 func checkBytes(b []byte) bool {
+	// trim leading zero bytes since Bytes() won't return them
+	// (was issue 12231)
+	for len(b) > 0 && b[0] == 0 {
+		b = b[1:]
+	}
 	b2 := new(Int).SetBytes(b).Bytes()
 	return bytes.Equal(b, b2)
 }