diff --git a/include/boost/config/platform/hpux.hpp b/include/boost/config/platform/hpux.hpp
index 77669461..4f2cf377 100644
--- a/include/boost/config/platform/hpux.hpp
+++ b/include/boost/config/platform/hpux.hpp
@@ -22,6 +22,13 @@
 #define BOOST_HAS_UNISTD_H
 #include <boost/config/posix_features.hpp>
 
+// HPUX has an incomplete pthreads implementation, so it doesn't
+// define _POSIX_THREADS, but it might be enough to implement
+// Boost.Threads.
+#if !defined(BOOST_HAS_PTHREADS) && defined(_POSIX_THREAD_ATTR_STACKADDR)
+# define BOOST_HAS_PTHREADS 
+#endif
+
 #ifndef BOOST_HAS_GETTIMEOFDAY
 // gettimeofday is always available
 #define BOOST_HAS_GETTIMEOFDAY