diff --git a/src/regex_debug.cpp b/src/regex_debug.cpp
index 5d898398..b6022e6f 100644
--- a/src/regex_debug.cpp
+++ b/src/regex_debug.cpp
@@ -23,6 +23,8 @@
 
 #include <boost/re_detail/regex_config.hpp>
 #include <boost/re_detail/regex_raw_buffer.hpp>
+#include <boost/regex.hpp>
+#include <ostream>
 
 #ifdef BOOST_MSVC
 #include <crtdbg.h>
@@ -30,6 +32,14 @@
 
 #ifdef BOOST_RE_DEBUG
 
+namespace boost { namespace re_detail {
+ostream& operator<<(ostream& s, syntax_element_type x)
+{
+    return s << static_cast<unsigned long>(x);
+}
+}} // namespace boost::re_detail
+
+
 namespace {
 
 char b1[32] = {0,};