diff --git a/nixd/libutil/include/nixd/util/AutoCloseFD.h b/nixd/libutil/include/nixd/util/AutoCloseFD.h
index 8b72125b5..018a67b16 100644
--- a/nixd/libutil/include/nixd/util/AutoCloseFD.h
+++ b/nixd/libutil/include/nixd/util/AutoCloseFD.h
@@ -1,7 +1,6 @@
 #pragma once
 
 #include <cerrno>
-#include <optional>
 
 namespace nixd::util {
 
diff --git a/nixd/libutil/include/nixd/util/AutoHUPPID.h b/nixd/libutil/include/nixd/util/AutoHUPPID.h
index 6a7383238..0c1a20126 100644
--- a/nixd/libutil/include/nixd/util/AutoHUPPID.h
+++ b/nixd/libutil/include/nixd/util/AutoHUPPID.h
@@ -1,6 +1,5 @@
-#include <csignal>
-
 #include <sched.h>
+#include <signal.h> // NOLINT(modernize-deprecated-headers)
 
 namespace nixd::util {
 
diff --git a/nixd/tools/nixd/src/NixTU.h b/nixd/tools/nixd/src/NixTU.h
index 7402fea44..1ac7d7a2b 100644
--- a/nixd/tools/nixd/src/NixTU.h
+++ b/nixd/tools/nixd/src/NixTU.h
@@ -5,6 +5,10 @@
 #include "nixf/Basic/Diagnostic.h"
 #include "nixf/Basic/Nodes/Basic.h"
 
+#include <memory>
+#include <optional>
+#include <vector>
+
 namespace nixd {
 
 /// \brief Holds analyzed information about a document.