diff --git a/introspection.hpp b/introspection.hpp
index 4aeab3f6..c4474fdc 100644
--- a/introspection.hpp
+++ b/introspection.hpp
@@ -23,10 +23,11 @@
 #include <array>
 #include <cstddef>
 #include <cstdint>
+#include <experimental/filesystem>
+#include <ostream>
 #include <string>
 #include <tuple>
 #include <utility>
-#include <experimental/filesystem>
 
 
 namespace util {