diff --git a/src/served/response.cpp b/src/served/response.cpp
index fd37843..6cbd4f8 100644
--- a/src/served/response.cpp
+++ b/src/served/response.cpp
@@ -55,7 +55,7 @@ response::set_header(std::string const& header, std::string const& value)
 
 	std::transform(header.begin(), header.end(), mut_header.begin(), ::tolower);
 
-	_headers[mut_header] = header_pair(header, value);
+	_headers.emplace(std::make_pair(mut_header, header_pair(header, value)));
 }
 
 void
diff --git a/src/served/response.hpp b/src/served/response.hpp
index e9dcb53..34aa029 100644
--- a/src/served/response.hpp
+++ b/src/served/response.hpp
@@ -47,7 +47,7 @@ namespace served {
 class response
 {
 	typedef std::tuple<std::string, std::string> header_pair;
-	typedef std::map<std::string, header_pair>   header_list;
+	typedef std::multimap<std::string, header_pair>   header_list;
 
 	int               _status;
 	header_list       _headers;