diff --git a/auth_algo.hpp b/auth_algo.hpp
index 5bf1a1e..894a853 100644
--- a/auth_algo.hpp
+++ b/auth_algo.hpp
@@ -4,6 +4,7 @@
 #include "integrity_algo.hpp"
 
 #include <array>
+#include <cstddef>
 #include <string>
 #include <vector>
 
diff --git a/command/rakp12.hpp b/command/rakp12.hpp
index b615c7b..c19853f 100644
--- a/command/rakp12.hpp
+++ b/command/rakp12.hpp
@@ -3,6 +3,7 @@
 #include "comm_module.hpp"
 #include "message_handler.hpp"
 
+#include <cstddef>
 #include <vector>
 
 namespace command
diff --git a/command_table.hpp b/command_table.hpp
index b51da9d..e882300 100644
--- a/command_table.hpp
+++ b/command_table.hpp
@@ -4,6 +4,7 @@
 
 #include <ipmid/api.h>
 
+#include <cstddef>
 #include <functional>
 #include <map>
 
diff --git a/integrity_algo.hpp b/integrity_algo.hpp
index 0dd4a91..cdeb617 100644
--- a/integrity_algo.hpp
+++ b/integrity_algo.hpp
@@ -3,6 +3,7 @@
 #include "rmcp.hpp"
 
 #include <array>
+#include <cstddef>
 #include <vector>
 
 namespace cipher
diff --git a/main.hpp b/main.hpp
index 6aa3a3f..7c78554 100644
--- a/main.hpp
+++ b/main.hpp
@@ -5,6 +5,7 @@
 #include "sol/sol_manager.hpp"
 
 #include <command_table.hpp>
+#include <cstddef>
 #include <sdbusplus/asio/connection.hpp>
 #include <sessions_manager.hpp>
 #include <tuple>
diff --git a/message.hpp b/message.hpp
index ebad490..738652c 100644
--- a/message.hpp
+++ b/message.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cstddef>
 #include <memory>
 #include <numeric>
 #include <vector>
diff --git a/message_parsers.hpp b/message_parsers.hpp
index 489eb23..5738c43 100644
--- a/message_parsers.hpp
+++ b/message_parsers.hpp
@@ -3,6 +3,8 @@
 #include "message.hpp"
 #include "session.hpp"
 
+#include <cstddef>
+
 namespace message
 {
 
diff --git a/rmcp.hpp b/rmcp.hpp
index 04d06d9..b18809a 100644
--- a/rmcp.hpp
+++ b/rmcp.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <array>
+#include <cstddef>
 #include <cstdint>
 
 namespace rmcp
diff --git a/sol/console_buffer.hpp b/sol/console_buffer.hpp
index 51383cf..dbb75c9 100644
--- a/sol/console_buffer.hpp
+++ b/sol/console_buffer.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <algorithm>
+#include <cstddef>
 #include <cstdint>
 #include <deque>
 #include <vector>
diff --git a/sol/sol_context.hpp b/sol/sol_context.hpp
index a857c7f..a071892 100644
--- a/sol/sol_context.hpp
+++ b/sol/sol_context.hpp
@@ -5,6 +5,7 @@
 
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/steady_timer.hpp>
+#include <cstddef>
 
 namespace sol
 {
diff --git a/sol/sol_manager.hpp b/sol/sol_manager.hpp
index 6a5887b..74ce8e9 100644
--- a/sol/sol_manager.hpp
+++ b/sol/sol_manager.hpp
@@ -6,6 +6,7 @@
 
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/local/stream_protocol.hpp>
+#include <cstddef>
 #include <map>
 #include <memory>
 #include <string>