diff --git a/src/w32_regex_traits.cpp b/src/w32_regex_traits.cpp
index 76d1f3e3..16e0a9f5 100644
--- a/src/w32_regex_traits.cpp
+++ b/src/w32_regex_traits.cpp
@@ -357,6 +357,7 @@ void BOOST_RE_CALL w32_traits_base::do_free()
    BOOST_RE_GUARD_STACK
    delete[] pclasses;
    delete pcoll_names;
+   delete syntax;
    if(hresmod)
    {
       FreeLibrary(hresmod);