Index: uspace/lib/cpp/src/thread.cpp
===================================================================
--- uspace/lib/cpp/src/thread.cpp	(revision 1df01656e67d5c3fbe6c5c8a4decfd12507b7334)
+++ uspace/lib/cpp/src/thread.cpp	(revision 4fe4ea621ef8746f43a02d11efbfa7e5478577dd)
@@ -42,5 +42,5 @@
         if (joinable())
         {
-            if (joinable_wrapper_)
+            if (joinable_wrapper_ && !joinable_wrapper_->detached())
             {
                 joinable_wrapper_->join();