diff --git a/include/evalhyd/evald.hpp b/include/evalhyd/evald.hpp
index 88e0868ad057731c770ffe530a799082974ab658..4e45cf62ef4d52c5f742f3e88a12b4e462969313 100644
--- a/include/evalhyd/evald.hpp
+++ b/include/evalhyd/evald.hpp
@@ -167,7 +167,7 @@ namespace evalhyd
                     xtl::missing<double>(),
             const xt::xexpression<XB2>& t_msk = XB2({}),
             const xt::xtensor<std::array<char, 32>, 1>& m_cdt = {},
-            xtl::xoptional<const std::unordered_map<std::string, int>> bootstrap =
+            xtl::xoptional<const std::unordered_map<std::string, int>, bool> bootstrap =
                     xtl::missing<const std::unordered_map<std::string, int>>(),
             const std::vector<std::string>& dts = {}
     )
diff --git a/include/evalhyd/evalp.hpp b/include/evalhyd/evalp.hpp
index 02505cb8f2bb2d72dc112dc8c94e2961b3700b1a..1a9e14bb7ac4e7c7364638883336e06deef48bb7 100644
--- a/include/evalhyd/evalp.hpp
+++ b/include/evalhyd/evalp.hpp
@@ -145,7 +145,7 @@ namespace evalhyd
             const xt::xexpression<XD2>& q_thr = XD2({}),
             const xt::xexpression<XB4>& t_msk = XB4({}),
             const xt::xtensor<std::array<char, 32>, 2>& m_cdt = {},
-            xtl::xoptional<const std::unordered_map<std::string, int>> bootstrap =
+            xtl::xoptional<const std::unordered_map<std::string, int>, bool> bootstrap =
                     xtl::missing<const std::unordered_map<std::string, int>>(),
             const std::vector<std::string>& dts = {}
     )