Comparison operators not defined for struct containing sequence

module M
{
  sequence<string> StringSeq;

  struct S
  {
    StringSeq tags;
  };
};

#include "Test.h"

int main()
{
  M::S a, b;
  return a == b;
}

CXX=g++
main.cpp: In function 'int main()':
main.cpp:6: error: no match for 'operator==' in 'a == b'
gmake: *** [all] Error 1

CXX=clang++
main.cpp:6:12: error: invalid operands to binary expression ('M::S' and 'M::S')
  return a == b;
         ~ ^  ~
1 error generated.
*** [all] Error code 1