[boost] [unordered_map] assert fail

I got an assert fail on a call to: return _map.insert(std::make_pair(newKey, value.second)); The assertion was in delete_buckets() BOOST_ASSERT(!this->size_); Here is a stack trace: #0 0x00007f3b7c645945 in raise () from /lib64/libc.so.6 #1 0x00007f3b7c646f21 in abort () from /lib64/libc.so.6 #2 0x00007f3b7c63e810 in __assert_fail () from /lib64/libc.so.6 #3 0x000000000075d59f in boost::unordered::detail::buckets >, boost::unordered::detail::ptr_bucket, boost::unordered::detail::ptr_node >, boost::unordered::detail::mix64_policy<unsigned long> >::delete_buckets (this=0x7f3b772ac0b0) at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/detail/buckets.hpp:834 #4 0x000000000075d125 in boost::unordered::detail::buckets >, boost::unordered::detail::ptr_bucket, boost::unordered::detail::ptr_node >, boost::unordered::detail::mix64_policy<unsigned long> >::~buckets (this=0x7f3b772ac0b0, __in_chrg=<optimized out>) at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/detail/buckets.hpp:805 #5 0x000000000075cebe in boost::unordered::detail::table_impl >, char const*, Spl::Market::Symbol*, Spl::String::MapSpl::Market::Symbol*::HashFunction, Spl::String::MapSpl::Market::Symbol*::Predicate> >::rehash_impl (this=0xfd1670, num_buckets=64) at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/detail/unique.hpp:746 #6 0x000000000075c915 in boost::unordered::detail::table >, char const*, Spl::Market::Symbol*, Spl::String::MapSpl::Market::Symbol*::HashFunction, Spl::String::MapSpl::Market::Symbol*::Predicate> >::reserve_for_insert (this=0xfd1670, size=33) at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/detail/table.hpp:413 #7 0x000000000075c48b in boost::unordered::detail::table_impl >, char const*, Spl::Market::Symbol*, Spl::String::MapSpl::Market::Symbol*::HashFunction, Spl::String::MapSpl::Market::Symbol*::Predicate>

::emplace_impl >(char const* const&, std::pair&&) (this=0xfd1670, k=@0x7f3b772ac360: 0x10f0da40 "XJO.5025P13.AX") at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/detail/unique.hpp:464 #8 0x000000000075c0a1 in boost::unordered::detail::table_impl >, char const*, Spl::Market::Symbol*, Spl::String::MapSpl::Market::Symbol*::HashFunction, Spl::String::MapSpl::Market::Symbol*::Predicate> ::emplace (std::pair&&) (this=0xfd1670) at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/detail/unique.hpp:430 #9 0x000000000075bebf in boost::unordered::unordered_mapSpl::Market::Symbol*::HashFunction, Spl::String::MapSpl::Market::Symbol*::Predicate, std::allocator > ::emplace (std::pair&&) (this=0xfd1670) at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/unordered_map.hpp:239 #10 0x000000000075bcf0 in boost::unordered::unordered_mapSpl::Market::Symbol*::HashFunction, Spl::String::MapSpl::Market::Symbol*::Predicate, std::allocator > ::insert(std::pair&&) (this=0xfd1670, x=...) at /hostname/trading/sdk/include/boost-1.51.0/boost/unordered/unordered_map.hpp:388