diff --git a/utilite/include/rtabmap/utilite/UStl.h b/utilite/include/rtabmap/utilite/UStl.h
index c343d939..560be22c 100644
--- a/utilite/include/rtabmap/utilite/UStl.h
+++ b/utilite/include/rtabmap/utilite/UStl.h
@@ -26,6 +26,7 @@
 #include <vector>
 #include <string>
 #include <algorithm>
+#include <stdlib.h>
 
 /**
  * \file UStl.h