diff --git a/.clang-format b/.clang-format
index 8e76392ad..17d93e85e 100644
--- a/.clang-format
+++ b/.clang-format
@@ -65,7 +65,7 @@ IncludeBlocks: Regroup
 IncludeCategories:
   # By default, first include the 'main' header file related to source file
   # Then include every 'system' headers (i.e. in <>)
-  - Regex:           '<[^Q][[:alnum:]]+(\.h)?>'
+  - Regex:           '<[^Q][[:alnum:]_]+(\.h)?>'
     Priority:        10
   # Then include '3rd party' headers 
   - Regex:           '<[[:alnum:]/._]+>'
diff --git a/ACore/src/ecflow/core/Str.hpp b/ACore/src/ecflow/core/Str.hpp
index 49e15e5fe..ca4da7070 100644
--- a/ACore/src/ecflow/core/Str.hpp
+++ b/ACore/src/ecflow/core/Str.hpp
@@ -14,10 +14,10 @@
 #include <cstring>
 #include <limits>
 #include <string>
+#include <string_view>
 #include <vector>
 
 #include <boost/algorithm/string.hpp>
-#include <string_view>
 
 namespace ecf {
 
diff --git a/ACore/src/ecflow/core/StringSplitter.hpp b/ACore/src/ecflow/core/StringSplitter.hpp
index 621ab7bb6..b5a0aa333 100644
--- a/ACore/src/ecflow/core/StringSplitter.hpp
+++ b/ACore/src/ecflow/core/StringSplitter.hpp
@@ -12,9 +12,8 @@
 #define ecflow_core_StringSplitter_HPP
 
 #include <string>
-#include <vector>
-
 #include <string_view>
+#include <vector>
 
 namespace ecf {
 
diff --git a/ACore/src/ecflow/core/WhiteListFile.hpp b/ACore/src/ecflow/core/WhiteListFile.hpp
index 786f85d9e..1041ff5de 100644
--- a/ACore/src/ecflow/core/WhiteListFile.hpp
+++ b/ACore/src/ecflow/core/WhiteListFile.hpp
@@ -16,9 +16,8 @@
 ///
 
 #include <string>
-#include <vector>
-
 #include <unordered_map>
+#include <vector>
 
 // ----------------------------------------------------------------
 // The whiteList file, is used to indicate users who are allowed
diff --git a/ACore/src/ecflow/core/cereal_optional_nvp.hpp b/ACore/src/ecflow/core/cereal_optional_nvp.hpp
index b9c16fba3..c5f802004 100644
--- a/ACore/src/ecflow/core/cereal_optional_nvp.hpp
+++ b/ACore/src/ecflow/core/cereal_optional_nvp.hpp
@@ -41,9 +41,10 @@
 /// };
 ///
 
+#include <type_traits> // for std::enable_if_t
+
 #include <cereal/cereal.hpp>
 #include <cereal/details/traits.hpp>
-#include <type_traits> // for std::enable_if_t
 
 namespace cereal {
 class JSONInputArchive;
diff --git a/ANode/src/ecflow/node/Defs.hpp b/ANode/src/ecflow/node/Defs.hpp
index 4eb37a8d1..96fa82a17 100644
--- a/ANode/src/ecflow/node/Defs.hpp
+++ b/ANode/src/ecflow/node/Defs.hpp
@@ -24,9 +24,8 @@
 #include <cstdint>
 #include <iosfwd>
 #include <set>
-#include <vector>
-
 #include <unordered_map>
+#include <vector>
 
 #include "ecflow/core/NOrder.hpp"
 #include "ecflow/core/NState.hpp"
diff --git a/ANode/src/ecflow/node/ExprDuplicate.cpp b/ANode/src/ecflow/node/ExprDuplicate.cpp
index 0434f30a5..d0f82eb4d 100644
--- a/ANode/src/ecflow/node/ExprDuplicate.cpp
+++ b/ANode/src/ecflow/node/ExprDuplicate.cpp
@@ -11,7 +11,6 @@
 #include "ecflow/node/ExprDuplicate.hpp"
 
 #include <iostream>
-
 #include <unordered_map>
 
 #include "ecflow/core/Ecf.hpp"
diff --git a/ANode/src/ecflow/node/parser/DefsStructureParser.hpp b/ANode/src/ecflow/node/parser/DefsStructureParser.hpp
index 6d7884036..cc08c74aa 100644
--- a/ANode/src/ecflow/node/parser/DefsStructureParser.hpp
+++ b/ANode/src/ecflow/node/parser/DefsStructureParser.hpp
@@ -13,9 +13,8 @@
 
 #include <stack>
 #include <string>
-#include <vector>
-
 #include <unordered_map>
+#include <vector>
 
 #include "ecflow/core/File_r.hpp"
 #include "ecflow/core/PrintStyle.hpp"
diff --git a/ANode/src/ecflow/node/parser/Parser.hpp b/ANode/src/ecflow/node/parser/Parser.hpp
index 5e7ececfe..56a482409 100644
--- a/ANode/src/ecflow/node/parser/Parser.hpp
+++ b/ANode/src/ecflow/node/parser/Parser.hpp
@@ -13,9 +13,8 @@
 
 #include <stack>
 #include <string>
-#include <vector>
-
 #include <unordered_map>
+#include <vector>
 
 class DefsStructureParser;
 class Node;
diff --git a/Base/src/ecflow/base/cts/ClientToServerCmd.hpp b/Base/src/ecflow/base/cts/ClientToServerCmd.hpp
index b78c149bd..b8e6a0194 100644
--- a/Base/src/ecflow/base/cts/ClientToServerCmd.hpp
+++ b/Base/src/ecflow/base/cts/ClientToServerCmd.hpp
@@ -15,8 +15,8 @@
 
 #include "ecflow/base/Cmd.hpp"
 #include "ecflow/core/PrintStyle.hpp"
-#include "ecflow/node/NodeFwd.hpp"
 #include "ecflow/core/Serialization.hpp"
+#include "ecflow/node/NodeFwd.hpp"
 
 class AbstractServer;
 class AbstractClientEnv;
diff --git a/Http/src/ecflow/http/ApiV1Impl.cpp b/Http/src/ecflow/http/ApiV1Impl.cpp
index 049133b38..be7a8caef 100644
--- a/Http/src/ecflow/http/ApiV1Impl.cpp
+++ b/Http/src/ecflow/http/ApiV1Impl.cpp
@@ -10,12 +10,11 @@
 
 #include "ecflow/http/ApiV1Impl.hpp"
 
+#include <condition_variable>
 #include <mutex>
 #include <string>
 #include <thread>
 
-#include <condition_variable>
-
 #include "ecflow/core/Child.hpp"
 #include "ecflow/core/Converter.hpp"
 #include "ecflow/core/Str.hpp"
diff --git a/Http/src/ecflow/http/TokenStorage.cpp b/Http/src/ecflow/http/TokenStorage.cpp
index 7f84b430a..764fb5080 100644
--- a/Http/src/ecflow/http/TokenStorage.cpp
+++ b/Http/src/ecflow/http/TokenStorage.cpp
@@ -15,13 +15,13 @@
     #include <atomic> // shared mutex only with c++14
     #include <fstream>
     #include <iomanip>
+    #include <shared_mutex>
     #include <sstream>
     #include <thread>
 
     #include <openssl/evp.h>
     #include <openssl/hmac.h>
     #include <openssl/sha.h>
-    #include <shared_mutex>
 
     #include "ecflow/core/Filesystem.hpp"
     #include "ecflow/core/Str.hpp"
diff --git a/Udp/src/ecflow/udp/UDPServerEnvironment.hpp b/Udp/src/ecflow/udp/UDPServerEnvironment.hpp
index 783d24318..3f3a962f5 100644
--- a/Udp/src/ecflow/udp/UDPServerEnvironment.hpp
+++ b/Udp/src/ecflow/udp/UDPServerEnvironment.hpp
@@ -13,9 +13,8 @@
 
 #include <optional>
 #include <string>
-#include <vector>
-
 #include <unordered_map>
+#include <vector>
 
 #include "ecflow/core/Converter.hpp"