diff --git a/example/kalman/ukf-nonlinear-example.cpp b/example/kalman/ukf-nonlinear-example.cpp
index c185c8d8ef..07f9e3bd9b 100644
--- a/example/kalman/ukf-nonlinear-example.cpp
+++ b/example/kalman/ukf-nonlinear-example.cpp
@@ -80,6 +80,8 @@
    the interval \f$[- \pi ; \pi ]\f$ .
 */
 
+#include <iostream>
+
 // UKF includes
 #include <visp3/core/vpUKSigmaDrawerMerwe.h>
 #include <visp3/core/vpUnscentedKalman.h>