diff --git a/src/array.hpp b/src/array.hpp
index e02f268927d1b2e84fda482a0ddab6e0ab86b3e6..3bfaec5d04cb479845a1a76f01969430af9a9640 100644
--- a/src/array.hpp
+++ b/src/array.hpp
@@ -410,7 +410,7 @@ public:
             static_assert(sizeof...(idxs) <= Shape::ndim,
                           "number of indices must be smaller than the number of dimensions");
 
-            const std::array<size_t, Shape::ndim> m{idxs...};
+            const std::array<size_t, Shape::ndim> m{static_cast<size_t>(idxs)...};
             size_t idx = 0;
 
             for (size_t i = 0; i < sizeof...(idxs); ++i) {