diff --git a/client_http.hpp b/client_http.hpp
index 084e1d6..20eaca8 100644
--- a/client_http.hpp
+++ b/client_http.hpp
@@ -2,12 +2,11 @@
 #define CLIENT_HTTP_HPP
 
 #include "utility.hpp"
+#include <limits>
 #include <mutex>
 #include <random>
 #include <unordered_set>
 #include <vector>
-#include <limits>
-#include <cstddef>
 
 #ifdef USE_STANDALONE_ASIO
 #include <asio.hpp>
diff --git a/client_https.hpp b/client_https.hpp
index 9fe2c3d..017cbf9 100644
--- a/client_https.hpp
+++ b/client_https.hpp
@@ -2,7 +2,6 @@
 #define CLIENT_HTTPS_HPP
 
 #include "client_http.hpp"
-#include <cstddef>
 
 #ifdef USE_STANDALONE_ASIO
 #include <asio/ssl.hpp>
diff --git a/server_http.hpp b/server_http.hpp
index 8540542..458260a 100644
--- a/server_http.hpp
+++ b/server_http.hpp
@@ -4,13 +4,12 @@
 #include "utility.hpp"
 #include <functional>
 #include <iostream>
+#include <limits>
 #include <map>
 #include <mutex>
 #include <sstream>
 #include <thread>
 #include <unordered_set>
-#include <limits>
-#include <cstddef>
 
 #ifdef USE_STANDALONE_ASIO
 #include <asio.hpp>
diff --git a/server_https.hpp b/server_https.hpp
index f38b727..8b44df3 100644
--- a/server_https.hpp
+++ b/server_https.hpp
@@ -10,7 +10,6 @@
 #endif
 
 #include <algorithm>
-#include <cstddef>
 #include <openssl/ssl.h>
 
 namespace SimpleWeb {
diff --git a/utility.hpp b/utility.hpp
index ecd4dd8..2af49e7 100644
--- a/utility.hpp
+++ b/utility.hpp
@@ -7,7 +7,6 @@
 #include <memory>
 #include <string>
 #include <unordered_map>
-#include <cstddef>
 
 namespace SimpleWeb {
   inline bool case_insensitive_equal(const std::string &str1, const std::string &str2) noexcept {