diff --git a/lib/cpp/src/concurrency/PosixThreadFactory.cpp b/lib/cpp/src/concurrency/PosixThreadFactory.cpp
index 70204f1..6924aa6 100644
--- a/lib/cpp/src/concurrency/PosixThreadFactory.cpp
+++ b/lib/cpp/src/concurrency/PosixThreadFactory.cpp
@@ -156,7 +156,13 @@
          cause the process to run out of thread resources.
          We're beyond the point of throwing an exception.  Not clear how
          best to handle this. */
-      detached_ = pthread_join(pthread_, &ignore) == 0;
+      int res = pthread_join(pthread_, &ignore);
+      detached_ = (res == 0);
+      if (res != 0) {
+        GlobalOutput.printf("PthreadThread::join(): fail with code %d", res);
+      }
+    } else {
+      GlobalOutput.printf("PthreadThread::join(): detached thread");
     }
   }