diff --git a/Examples/ROS/ORB_SLAM2/CMakeLists.txt b/Examples/ROS/ORB_SLAM2/CMakeLists.txt
index 7cbf71c199..572ad96b4d 100644
--- a/Examples/ROS/ORB_SLAM2/CMakeLists.txt
+++ b/Examples/ROS/ORB_SLAM2/CMakeLists.txt
@@ -55,6 +55,7 @@ ${Pangolin_LIBRARIES}
 ${PROJECT_SOURCE_DIR}/../../../Thirdparty/DBoW2/lib/libDBoW2.so
 ${PROJECT_SOURCE_DIR}/../../../Thirdparty/g2o/lib/libg2o.so
 ${PROJECT_SOURCE_DIR}/../../../lib/libORB_SLAM2.so
+-lboost_system
 )
 
 # Node for monocular camera
diff --git a/include/System.h b/include/System.h
index b377b453d1..0e6be19c0d 100644
--- a/include/System.h
+++ b/include/System.h
@@ -24,6 +24,7 @@
 
 #include<string>
 #include<thread>
+#include<unistd.h>
 #include<opencv2/core/core.hpp>
 
 #include "Tracking.h"