diff --git a/include/magic_enum.hpp b/include/magic_enum.hpp
index ad25e84..f17414a 100644
--- a/include/magic_enum.hpp
+++ b/include/magic_enum.hpp
@@ -40,6 +40,7 @@
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
+#include <functional>
 #include <limits>
 #include <type_traits>
 #include <utility>