diff --git a/util/threadpool_imp.cc b/util/threadpool_imp.cc
index c05c54101..19e975788 100644
--- a/util/threadpool_imp.cc
+++ b/util/threadpool_imp.cc
@@ -24,6 +24,7 @@
 #include <atomic>
 #include <condition_variable>
 #include <mutex>
+#include <stdlib.h>
 #include <thread>
 #include <vector>