diff --git a/examples/3d_point_cloud_ex.cpp b/examples/3d_point_cloud_ex.cpp
index 3cb7d09fa..f64a68976 100644
--- a/examples/3d_point_cloud_ex.cpp
+++ b/examples/3d_point_cloud_ex.cpp
@@ -9,8 +9,10 @@
 
 #include <dlib/gui_widgets.h>
 #include <dlib/image_transforms.h>
+#include <cmath>
 
 using namespace dlib;
+using namespace std;
 
 // ----------------------------------------------------------------------------------------