diff --git a/src/system/libroot/posix/pthread/pthread.cpp b/src/system/libroot/posix/pthread/pthread.cpp
index 4c5104a..71e5eca 100644
--- a/src/system/libroot/posix/pthread/pthread.cpp
+++ b/src/system/libroot/posix/pthread/pthread.cpp
@@ -191,6 +191,9 @@ pthread_join(pthread_t thread, void** _value)
 
 	if (_value != NULL)
 		*_value = thread->exit_value;
+	
+	if(thread->flags & THREAD_DETACHED)
+		return EINVAL;;
 
 	if ((atomic_or(&thread->flags, THREAD_DETACHED) & THREAD_DEAD) != 0)
 		free(thread);