diff --git a/include/boost/crypt/hash/md5.hpp b/include/boost/crypt/hash/md5.hpp
index 0295dcb..007e8c3 100644
--- a/include/boost/crypt/hash/md5.hpp
+++ b/include/boost/crypt/hash/md5.hpp
@@ -9,6 +9,7 @@
 #include <boost/crypt/utility/bit.hpp>
 
 #include <algorithm>
+#include <iterator>
 #include <array>
 #include <vector>
 #include <string>