diff --git a/src/test_hashes.cpp b/src/test_hashes.cpp
index c796dbcad..5683c8727 100644
--- a/src/test_hashes.cpp
+++ b/src/test_hashes.cpp
@@ -1,11 +1,11 @@
 #include <algorithm>
+#include <cstddef>
+#include <cstdint>
 #include <fstream>
 #include <iomanip>
 #include <iostream>
 #include <iterator>
 #include <map>
-#include <cstddef>
-#include <cstdint>
 #include <string>
 #include <tuple>
 #include <utility>
diff --git a/tests/root_io/read_frame_legacy_root.cpp b/tests/root_io/read_frame_legacy_root.cpp
index f571e0190..90cc3b13b 100644
--- a/tests/root_io/read_frame_legacy_root.cpp
+++ b/tests/root_io/read_frame_legacy_root.cpp
@@ -1,5 +1,5 @@
-#include <iostream>
 #include <cstddef>
+#include <iostream>
 #include <stdexcept>
 #include <string>
 
diff --git a/tests/root_io/read_frame_root_multiple.cpp b/tests/root_io/read_frame_root_multiple.cpp
index c24b900a5..faa4c6154 100644
--- a/tests/root_io/read_frame_root_multiple.cpp
+++ b/tests/root_io/read_frame_root_multiple.cpp
@@ -1,6 +1,6 @@
+#include <cstddef>
 #include <iostream>
 #include <memory>
-#include <cstddef>
 #include <string>
 #include <vector>
 
diff --git a/tests/root_io/relation_range.cpp b/tests/root_io/relation_range.cpp
index 710c4ffc3..d256b3f70 100644
--- a/tests/root_io/relation_range.cpp
+++ b/tests/root_io/relation_range.cpp
@@ -1,6 +1,6 @@
+#include <cstddef>
 #include <iostream>
 #include <sstream>
-#include <cstddef>
 #include <stdexcept>
 #include <string>
 #include <utility>
diff --git a/tests/sio_io/read_frame_legacy_sio.cpp b/tests/sio_io/read_frame_legacy_sio.cpp
index ed488908f..e3de22be9 100644
--- a/tests/sio_io/read_frame_legacy_sio.cpp
+++ b/tests/sio_io/read_frame_legacy_sio.cpp
@@ -1,6 +1,6 @@
+#include <cstddef>
 #include <iostream>
 #include <memory>
-#include <cstddef>
 #include <stdexcept>
 
 #include "podio/Frame.h"
diff --git a/tests/unittests/unittest.cpp b/tests/unittests/unittest.cpp
index 95473ea1f..f3d17ffa4 100644
--- a/tests/unittests/unittest.cpp
+++ b/tests/unittests/unittest.cpp
@@ -2,6 +2,7 @@
 #include <array>
 #include <catch2/matchers/catch_matchers.hpp>
 #include <compare>
+#include <cstddef>
 #include <cstdint>
 #include <filesystem>
 #include <iostream>
@@ -12,7 +13,6 @@
 #include <nlohmann/json_fwd.hpp>
 #include <set>
 #include <sstream>
-#include <cstddef>
 #include <stdexcept>
 #include <string>
 #include <thread>