diff --git a/test/engine/engine_util_solve_test.cc b/test/engine/engine_util_solve_test.cc
index 6e79dc41..dabc6024 100644
--- a/test/engine/engine_util_solve_test.cc
+++ b/test/engine/engine_util_solve_test.cc
@@ -17,6 +17,7 @@
 #include "src/engine/engine_util_solve.h"
 
 #include <random>
+#include <iomanip>
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>