diff --git a/include/gsl/span b/include/gsl/span
index 9d67fb6..36c8a8b 100644
--- a/include/gsl/span
+++ b/include/gsl/span
@@ -619,43 +619,43 @@ as_writeable_bytes(span<ElementType, Extent> s) GSL_NOEXCEPT
 // make_span() - Utility functions for creating spans
 //
 template <class ElementType>
-span<ElementType> make_span(ElementType* ptr, typename span<ElementType>::index_type count)
+constexpr span<ElementType> make_span(ElementType* ptr, typename span<ElementType>::index_type count)
 {
     return span<ElementType>(ptr, count);
 }
 
 template <class ElementType>
-span<ElementType> make_span(ElementType* firstElem, ElementType* lastElem)
+constexpr span<ElementType> make_span(ElementType* firstElem, ElementType* lastElem)
 {
     return span<ElementType>(firstElem, lastElem);
 }
 
 template <class ElementType, std::size_t N>
-span<ElementType, N> make_span(ElementType (&arr)[N])
+constexpr span<ElementType, N> make_span(ElementType (&arr)[N])
 {
     return span<ElementType, N>(arr);
 }
 
 template <class Container>
-span<typename Container::value_type> make_span(Container& cont)
+constexpr span<typename Container::value_type> make_span(Container& cont)
 {
     return span<typename Container::value_type>(cont);
 }
 
 template <class Container>
-span<const typename Container::value_type> make_span(const Container& cont)
+constexpr span<const typename Container::value_type> make_span(const Container& cont)
 {
     return span<const typename Container::value_type>(cont);
 }
 
 template <class Ptr>
-span<typename Ptr::element_type> make_span(Ptr& cont, std::ptrdiff_t count)
+constexpr span<typename Ptr::element_type> make_span(Ptr& cont, std::ptrdiff_t count)
 {
     return span<typename Ptr::element_type>(cont, count);
 }
 
 template <class Ptr>
-span<typename Ptr::element_type> make_span(Ptr& cont)
+constexpr span<typename Ptr::element_type> make_span(Ptr& cont)
 {
     return span<typename Ptr::element_type>(cont);
 }