diff --git a/Polynomial/test/Polynomial/test_polynomial.h b/Polynomial/test/Polynomial/test_polynomial.h
index 5141ffa239c..8a3bb3bbda9 100644
--- a/Polynomial/test/Polynomial/test_polynomial.h
+++ b/Polynomial/test/Polynomial/test_polynomial.h
@@ -298,6 +298,7 @@ void io() {
         // successful re-reading of output
         POLY p(NT(-3), NT(5), NT(0), NT(0), NT(-7), NT(9)), q;
         std::ostringstream os;
+        os.precision(17);
         os << p;
         std::istringstream is(os.str());
         is >> q;