diff --git a/source/gui/animation.cpp b/source/gui/animation.cpp
index c57984d1..c118ee51 100644
--- a/source/gui/animation.cpp
+++ b/source/gui/animation.cpp
@@ -677,6 +677,8 @@ namespace nana
 						thr = nullptr;
 				}
 
+				p->thr_variable = nullptr;
+
 				threads_.erase(i);
 				if (thr && thr->thread && thr->thread->joinable())
 					thr->thread->join();