diff --git a/include/loki/flex/flex_string_shell.h b/include/loki/flex/flex_string_shell.h
index 975f2ee..ecdfb7b 100644
--- a/include/loki/flex/flex_string_shell.h
+++ b/include/loki/flex/flex_string_shell.h
@@ -1305,8 +1305,12 @@ bool operator>=(const typename flex_string<E, T, A, S>::value_type* lhs,
     const flex_string<E, T, A, S>& rhs)
 { return !(lhs < rhs); }
 
-// subclause 21.3.7.8:
-//void swap(flex_string<E, T, A, S>& lhs, flex_string<E, T, A, S>& rhs);    // to do
+template <typename E, class T, class A, class S>
+inline void swap(flex_string<E, T, A, S>& lhs, flex_string<E, T, A, S>& rhs)
+{
+  // 21.3.7.8
+  lhs.swap(rhs);
+}
 
 template <typename E, class T, class A, class S>
 std::basic_istream<typename flex_string<E, T, A, S>::value_type,
diff --git a/test/flex_string/main.cpp b/test/flex_string/main.cpp
index e4b5c9e..d84c9d9 100644
--- a/test/flex_string/main.cpp
+++ b/test/flex_string/main.cpp
@@ -515,7 +515,7 @@ namespace Tests
   template<class String>
   String swap_string_string()
   {
-    using std::swap;
+    // 21.3.7.8
     String random1(RandomString<String>(MaxString<String>::value));
     String random2(RandomString<String>(MaxString<String>::value));
     swap(random1, random2);
@@ -525,7 +525,7 @@ namespace Tests
   template<class String>
   String swap_string_string__self()
   {
-    using std::swap;
+    // 21.3.7.8
     String random1(RandomString<String>(MaxString<String>::value));
     swap(random1, random1);
     return random1;
@@ -534,7 +534,7 @@ namespace Tests
   template<class String>
   String swap_string_string__selfcopy()
   {
-    using std::swap;
+    // 21.3.7.8
     String random1(RandomString<String>(MaxString<String>::value));
     String copy(random1);
     swap(random1, copy);
@@ -544,7 +544,7 @@ namespace Tests
   template<class String>
   String swap_string_string__selfcopy2()
   {
-    using std::swap;
+    // 21.3.7.8
     String random1(RandomString<String>(MaxString<String>::value));
     String copy(random1);
     swap(copy, random1);