diff --git a/lib/direct/Base.h b/lib/direct/Base.h
index 1f08fb513..2a72ff225 100644
--- a/lib/direct/Base.h
+++ b/lib/direct/Base.h
@@ -56,6 +56,7 @@ extern "C" {
 #include <memory>
 #include <set>
 #include <string>
+#include <functional>
 
 #include <stdexcept>