--- boost/thread/pthread/condition_variable_fwd.hpp.old	2015-04-18 05:56:34.000000000 -0400
+++ boost/thread/pthread/condition_variable_fwd.hpp	2017-04-20 04:09:26.656070060 -0400
@@ -32,9 +32,12 @@
     class condition_variable
     {
     private:
-#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+
+//#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+        // This data must be present so that with-and-without
+        // interrupts the structure is the same for ABI compatibility
         pthread_mutex_t internal_mutex;
-#endif
+//#endif
         pthread_cond_t cond;
 
     public:
@@ -55,31 +58,37 @@
       BOOST_THREAD_NO_COPYABLE(condition_variable)
         condition_variable()
         {
-#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+//#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+            // Even if it is not used, the internal_mutex exists (see
+            // above) and must be initialized (etc) in case some
+            // compilation units provide interruptions and others
+            // don't.
             int const res=pthread_mutex_init(&internal_mutex,NULL);
             if(res)
             {
                 boost::throw_exception(thread_resource_error(res, "boost::condition_variable::condition_variable() constructor failed in pthread_mutex_init"));
             }
-#endif
+//#endif
             int const res2=pthread_cond_init(&cond,NULL);
             if(res2)
             {
-#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+//#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+                // ditto
                 BOOST_VERIFY(!pthread_mutex_destroy(&internal_mutex));
-#endif
+//#endif
                 boost::throw_exception(thread_resource_error(res2, "boost::condition_variable::condition_variable() constructor failed in pthread_cond_init"));
             }
         }
         ~condition_variable()
         {
             int ret;
-#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+//#if defined BOOST_THREAD_PROVIDES_INTERRUPTIONS
+            // ditto
             do {
               ret = pthread_mutex_destroy(&internal_mutex);
             } while (ret == EINTR);
             BOOST_ASSERT(!ret);
-#endif
+//#endif
             do {
               ret = pthread_cond_destroy(&cond);
             } while (ret == EINTR);