diff --git a/.clang-format b/.clang-format
index 4752408333..164beac539 100644
--- a/.clang-format
+++ b/.clang-format
@@ -53,13 +53,13 @@ IncludeCategories:
   - Regex:           '^<(asiodns|asiolink|cc|config|config_backend|cryptolink|database|dhcp|dhcpsrv|dhcp_ddns|dns|eval|exceptions|hooks|http|log|mysql|pgsql|process|stats|testutils|util|yang|admin|agent|d2|dhcp4|dhcp6|keactrl|lfc|netconf|perfdhcp|shell|limits)/'
     Priority:        1
     # C++ standard library headers
-  - Regex:           '^<[[:alnum:]]>$'
+  - Regex:           '^<[_[:alnum:]]+>$'
     Priority:        2
     # boost headers
   - Regex:           '^<boost/'
     Priority:        3
     # C headers
-  - Regex:           '^<[[:alnum:]].h>$'
+  - Regex:           '^<[/_[:alnum:]]+\.h>$'
     Priority:        4
     # everything else
   - Regex:           '.*'