diff --git a/src/utils.hpp b/src/utils.hpp
index fc5f0fe..c345f15 100644
--- a/src/utils.hpp
+++ b/src/utils.hpp
@@ -6,6 +6,7 @@
 #include <chrono>
 #include <mutex>
 #include <random>
+#include <ostream>
 
 #include "types.hpp"