diff --git a/nonlib/Thread.C b/nonlib/Thread.C
index 6f2227b..6e5b953 100644
--- a/nonlib/Thread.C
+++ b/nonlib/Thread.C
@@ -129,7 +129,11 @@ Thread::cancel ( void )
 void
 Thread::join ( void )
 {
-    pthread_join( _thread, NULL );
+    if ( _thread != 0 )
+    {
+        /* not joined yet, go ahead. */
+        pthread_join( _thread, NULL );
+    }
     _thread = 0;
 }