diff --git a/src/util/io/reader.hpp b/src/util/io/reader.hpp
index d3058166..d0fbbe74 100644
--- a/src/util/io/reader.hpp
+++ b/src/util/io/reader.hpp
@@ -10,6 +10,7 @@
 
 #include <util/prec.hpp>
 #include <util/version.hpp>
+#include <unordered_map>
 
 template <typename T> class Defaultable;
 template <typename T> class Scriptable;
diff --git a/src/util/io/writer.hpp b/src/util/io/writer.hpp
index 5efb8130..cffb5bd7 100644
--- a/src/util/io/writer.hpp
+++ b/src/util/io/writer.hpp
@@ -10,6 +10,7 @@
 
 #include <util/prec.hpp>
 #include <wx/txtstrm.h>
+#include <unordered_map>
 
 template <typename T> class Defaultable;
 template <typename T> class Scriptable;