diff --git a/include/boost/archive/archive_exception.hpp b/include/boost/archive/archive_exception.hpp
index e95b6f15e..0e9dddff6 100644
--- a/include/boost/archive/archive_exception.hpp
+++ b/include/boost/archive/archive_exception.hpp
@@ -39,8 +39,11 @@ namespace archive {
 //////////////////////////////////////////////////////////////////////
 // exceptions thrown by archives
 //
+// The base is deliberately not virtual: a virtual one would give the
+// class an implicit vbase destructor, which cl and clang-cl expect to
+// find in different modules.  See issue #321.
 class BOOST_SYMBOL_VISIBLE archive_exception :
-    public virtual std::exception
+    public std::exception
 {
 private:
     char m_buffer[128];
diff --git a/include/boost/archive/xml_archive_exception.hpp b/include/boost/archive/xml_archive_exception.hpp
index 66be31f70..0ebb0a2ce 100644
--- a/include/boost/archive/xml_archive_exception.hpp
+++ b/include/boost/archive/xml_archive_exception.hpp
@@ -31,8 +31,10 @@ namespace archive {
 //////////////////////////////////////////////////////////////////////
 // exceptions thrown by xml archives
 //
+// The base is deliberately not virtual, for the reason given in
+// archive_exception.hpp.  See issue #321.
 class BOOST_SYMBOL_VISIBLE xml_archive_exception :
-    public virtual boost::archive::archive_exception
+    public boost::archive::archive_exception
 {
 public:
     typedef enum {