diff --git a/include/evalhyd/evald.hpp b/include/evalhyd/evald.hpp
index 45ff6591af894998e42063bf2a6b534db476f237..417f8beeb041d2bc820a0e05afdfe145bc2a0175 100644
--- a/include/evalhyd/evald.hpp
+++ b/include/evalhyd/evald.hpp
@@ -142,7 +142,7 @@ namespace evalhyd
             const xt::xtensor<double, 2>& q_prd,
             const std::vector<std::string>& metrics,
             const std::string& transform = "none",
-            const double exponent = 1,
+            double exponent = 1,
             double epsilon = -9,
             const xt::xtensor<bool, 2>& t_msk = {},
             const xt::xtensor<std::array<char, 32>, 1>& m_cdt = {},
diff --git a/src/determinist/evald.cpp b/src/determinist/evald.cpp
index 0ce84b6f9d6649c0f95b0ff8ac978552cc3c2df1..e6ec8dbede8cddb3876684acf9bb34a5152c4741 100644
--- a/src/determinist/evald.cpp
+++ b/src/determinist/evald.cpp
@@ -23,7 +23,7 @@ namespace evalhyd
             const xt::xtensor<double, 2>& q_prd,
             const std::vector<std::string>& metrics,
             const std::string& transform,
-            const double exponent,
+            double exponent,
             double epsilon,
             const xt::xtensor<bool, 2>& t_msk,
             const xt::xtensor<std::array<char, 32>, 1>& m_cdt,