diff --git a/CMakeLists.txt b/CMakeLists.txt
index de1c33a3ddb234071603bf5b7f4c36b6524a3f90..b5b4f6c6a56033fa1e951907cfb90e67a41c1131 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -23,8 +23,7 @@ if(NOT clang_tidy)
     message(STATUS "clang-tidy: Not found")
 else()
     message(STATUS "clang-tidy: ${clang_tidy}")
-    set(CMAKE_C_CLANG_TIDY "${clang_tidy}" "--header-filter=." "--checks=*" "--warnings-as-errors=*")
-    set(CMAKE_CXX_CLANG_TIDY "${clang_tidy}" "--header-filter=." "--checks=*" "--warnings-as-errors=*")
+    set(CMAKE_C_CLANG_TIDY "${clang_tidy}" "--header-filter=." "--checks=*,-llvm-include-order,-llvmlibc-restrict-system-libc-headers" "--warnings-as-errors=*")
 endif()
 
 add_subdirectory(src)
diff --git a/include/connection.h b/include/connection.h
index 0c36e48e3aae74477975424c6dece046a92e9df0..fb0c6c6d74806f42c380cea3f935867998145339 100644
--- a/include/connection.h
+++ b/include/connection.h
@@ -1,3 +1,5 @@
+#ifndef CONNECTION_H
+#define CONNECTION_H
 /**
  * @file connection.h
  * @author Timm Fitschen
@@ -12,3 +14,4 @@
  * @return 0 if everything is ok.
  */
 int configure_connection(char host[], int port);
+#endif
diff --git a/include/libcaosdbConfig.h.in b/include/libcaosdbConfig.h.in
index 2abf00b7d0bd9ceb3316f1d12d904faa4d720a19..de099a6773c3fd36c378f5ad79351ad7ee38163b 100644
--- a/include/libcaosdbConfig.h.in
+++ b/include/libcaosdbConfig.h.in
@@ -1,5 +1,8 @@
+#ifndef LIBCAOSDBCONFIG_H
+#define LIBCAOSDBCONFIG_H
 // clang-format off
 #define LIBCAOSDB_VERSION_MAJOR @libcaosdb_VERSION_MAJOR@
 #define LIBCAOSDB_VERSION_MINOR @libcaosdb_VERSION_MINOR@
 #define LIBCAOSDB_VERSION_PATCH @libcaosdb_VERSION_PATCH@
 // clang-format on
+#endif
diff --git a/src/caosdbcli.c b/src/caosdbcli.c
index fc10c4574868698344cb0791fb8c916ba06372e0..2d147f937e83387b4193bcbe23726671a242e6c3 100644
--- a/src/caosdbcli.c
+++ b/src/caosdbcli.c
@@ -9,6 +9,7 @@ int main(void) {
          LIBCAOSDB_VERSION_MINOR, LIBCAOSDB_VERSION_PATCH);
   printf("We don't miss the H of caos.\n");
 
+  // NOLINTNEXTLINE(cppcoreguidelines-avoid-magic-numbers, readability-magic-numbers)
   configure_connection("localhost", 8080);
 
   return 0;
diff --git a/src/connection.c b/src/connection.c
index 5c8ea1ef516f7ef6cc7465119bfcd05120cb448c..d8bef694c30ce40cdb31f201900d261e93a816e5 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -2,8 +2,9 @@
 #include <stdio.h>
 
 int configure_connection(char host[], int port) {
+  // NOLINTNEXTLINE(cppcoreguidelines-avoid-magic-numbers, readability-magic-numbers)
   if (port > 666 && port < 668) {
-    printf("667 - One step ahead of the Devil!");
+      printf("667 - One step ahead of the Devil!");
   }
   printf("Configure connection: %s:%d\n", host, port);
   return 0;
diff --git a/test/test_connection.c b/test/test_connection.c
index 8ee7520bfb3537d31e5be8ca722d94dc630cae26..80ae6b2a84c0108d3f886328fcc78db74d3c2521 100644
--- a/test/test_connection.c
+++ b/test/test_connection.c
@@ -1,9 +1,10 @@
-#include <setjmp.h>
-#include <stdarg.h>
+#include "connection.h"
+#include <setjmp.h> // IWYU pragma: keep
+#include <stdarg.h> // IWYU pragma: keep
 #include <stddef.h>
 #include <cmocka.h>
-#include "connection.h"
 
+// NOLINTNEXTLINE(misc-unused-parameters)
 static void test_configure_connection(void **state) {
   assert_int_equal(0, configure_connection("localhost", 8080));
 }