diff --git a/include/gsl/string_span b/include/gsl/string_span
index 33e096a..f2fbe83 100644
--- a/include/gsl/string_span
+++ b/include/gsl/string_span
@@ -26,6 +26,7 @@
 #include <cstdint>
 #include <cstring>
 #include <string>
+#include <type_traits>
 
 #ifdef _MSC_VER
 #pragma warning(push)