diff --git a/shared_ptr.h b/shared_ptr.h
index b291449..bd23979 100755
--- a/shared_ptr.h
+++ b/shared_ptr.h
@@ -1,5 +1,5 @@
 //---------------------------------------------------------------------------
-
+#include <cstdlib>
 #ifndef shared_ptrH
 #define shared_ptrH
 //---------------------------------------------------------------------------