diff --git a/src/tests/util/thread.cpp b/src/tests/util/thread.cpp
index 7373a7570e..8fe2ac9cf7 100644
--- a/src/tests/util/thread.cpp
+++ b/src/tests/util/thread.cpp
@@ -4,6 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 
 Author: Leonardo de Moura
 */
+#include <cstdlib>
 #include <thread>
 #include <iostream>
 #include <mutex>