diff --git a/include/boost/logic/tribool_io.hpp b/include/boost/logic/tribool_io.hpp
index a75146c..19eb944 100644
--- a/include/boost/logic/tribool_io.hpp
+++ b/include/boost/logic/tribool_io.hpp
@@ -201,6 +201,26 @@ operator<<(std::basic_ostream<CharT, Traits>& out, tribool x)
   return out;
 }
 
+/**
+ * \brief Writes the indeterminate tribool value to a stream.
+ *
+ * This routine outputs either the integer
+ * value 2 (if <tt>(out.flags() & std::ios_base::boolalpha) == 0</tt>)
+ * or the name of the indeterminate value. The name of the
+ * indeterminate value comes from the indeterminate_name facet (if it
+ * is defined in the output stream's locale), or from the
+ * get_default_indeterminate_name function (if it is not defined in the
+ * locale or if the C++ standard library implementation does not
+ * support locales).
+ *
+ * \returns @p out
+ */
+template<typename CharT, typename Traits>
+inline std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& out, 
+           bool (&)(tribool, detail::indeterminate_t))
+{ return out << tribool(indeterminate); } 
+
 /**
  * \brief Reads a tribool value from a stream.
  *
diff --git a/test/tribool_io_test.cpp b/test/tribool_io_test.cpp
index 2c059f7..d7254f1 100644
--- a/test/tribool_io_test.cpp
+++ b/test/tribool_io_test.cpp
@@ -44,6 +44,13 @@ int test_main(int, char*[])
             << std::endl;
   BOOST_CHECK(out.str() == "2");
 
+  // Output indeterminate (noboolalpha)
+  out.str(std::string());
+  out << indeterminate;
+  std::cout << "Output indeterminate (noboolalpha): " << out.str()
+            << std::endl;
+  BOOST_CHECK(out.str() == "2");
+
 #ifndef BOOST_NO_STD_LOCALE
   const std::numpunct<char>& punct =
     BOOST_USE_FACET(std::numpunct<char>, out.getloc());
@@ -71,6 +78,13 @@ int test_main(int, char*[])
             << std::endl;
   BOOST_CHECK(out.str() == "indeterminate");
 
+  // Output indeterminate (boolalpha - default name)
+  out.str(std::string());
+  out << std::boolalpha << indeterminate;
+  std::cout << "Output indeterminate (boolalpha - default name): " << out.str()
+            << std::endl;
+  BOOST_CHECK(out.str() == "indeterminate");
+
 #  if BOOST_WORKAROUND(BOOST_DINKUMWARE_STDLIB, == 1)
   // No template constructors, so we can't build the test locale
 #  else