diff --git a/unit_test/include/random_number_generator_test.hpp b/unit_test/include/random_number_generator_test.hpp
index 61f28ce..0248ddc 100644
--- a/unit_test/include/random_number_generator_test.hpp
+++ b/unit_test/include/random_number_generator_test.hpp
@@ -2,6 +2,7 @@
 #define RANDOM_NUMBER_GENERATOR_TEST_HPP
 
 #include <map>
+#include <iomanip>
 
 #include "../../include/qureg.hpp"