diff --git a/include/libimp/detect_plat.h b/include/libimp/detect_plat.h
index df3ac37..c445ed7 100644
--- a/include/libimp/detect_plat.h
+++ b/include/libimp/detect_plat.h
@@ -38,9 +38,12 @@
 // Compiler
 
 #if defined(_MSC_VER)
-# define LIBIMP_CC_MSVC
+# define LIBIMP_CC_MSVC      _MSC_VER
+# define LIBIMP_CC_MSVC_2015 1900
+# define LIBIMP_CC_MSVC_2017 1910
+# define LIBIMP_CC_MSVC_2019 1920
 #elif defined(__GNUC__)
-# define LIBIMP_CC_GNUC
+# define LIBIMP_CC_GNUC __GNUC__
 #else
 # error "This compiler is unsupported."
 #endif
diff --git a/include/libimp/span.h b/include/libimp/span.h
index b77cce3..36e43f5 100644
--- a/include/libimp/span.h
+++ b/include/libimp/span.h
@@ -91,7 +91,10 @@ private:
 public:
   constexpr span() noexcept = default;
   constexpr span(span const &) noexcept = default;
-  constexpr span & operator=(span const &) noexcept = default;
+#if (LIBIMP_CC_MSVC > LIBIMP_CC_MSVC_2015)
+  constexpr
+#endif
+  span & operator=(span const &) noexcept = default;
 
   template <typename It, 
             typename = detail::is_compatible_iter<T, It>>
@@ -128,7 +131,7 @@ public:
     : ptr_   (s.data())
     , extent_(s.size()) {}
 
-#ifdef LIBIMP_CPP_20
+#if defined(LIBIMP_CPP_20) || defined(__cpp_lib_span)
   template <typename U, std::size_t E,
             typename = detail::is_array_convertible<U, T>>
   constexpr span(std::span<U, E> const &s) noexcept