diff --git a/src/cli.cc b/src/cli.cc
index b978502..71de541 100644
--- a/src/cli.cc
+++ b/src/cli.cc
@@ -11,10 +11,9 @@
 
 #include <getopt.h>
 #include <limits.h>
+#include <string.h>
 #include <unistd.h>
 
-#include <memory>
-
 static const char* version = PROJECT_NAME " version " PROJECT_VERSION "\n";
 
 static const char* usage = 1 + R"raw(
diff --git a/src/ogg.cc b/src/ogg.cc
index af2931b..e7d981a 100644
--- a/src/ogg.cc
+++ b/src/ogg.cc
@@ -8,9 +8,9 @@
  * specialized layer above libogg and stdio.
  */
 
-#include "opustags.h"
+#include <opustags.h>
 
-#include <cstdio>
+#include <string.h>
 
 using namespace std::literals::string_literals;
 
diff --git a/src/opus.cc b/src/opus.cc
index 1531624..972adb0 100644
--- a/src/opus.cc
+++ b/src/opus.cc
@@ -22,11 +22,9 @@
  *
  */
 
-#include "opustags.h"
+#include <opustags.h>
 
-#include <cstdlib>
-#include <cstdio>
-#include <cstring>
+#include <string.h>
 
 #ifdef __APPLE__
 #include <libkern/OSByteOrder.h>
diff --git a/src/opustags.h b/src/opustags.h
index 53788b7..8f7b759 100644
--- a/src/opustags.h
+++ b/src/opustags.h
@@ -21,11 +21,11 @@
  *
  */
 
-#include <ogg/ogg.h>
+#pragma once
+
+#include <ogg/ogg.h>
+#include <stdio.h>
 
-#include <cstdint>
-#include <cstdio>
-#include <cstring>
 #include <list>
 #include <memory>
 #include <string>
diff --git a/t/cli.cc b/t/cli.cc
index 9b2e1aa..4a5d07d 100644
--- a/t/cli.cc
+++ b/t/cli.cc
@@ -1,6 +1,8 @@
 #include <opustags.h>
 #include "tap.h"
 
+#include <string.h>
+
 const char *user_comments = R"raw(
 TITLE=a b c
 
diff --git a/t/ogg.cc b/t/ogg.cc
index a55be2f..8dfaf07 100644
--- a/t/ogg.cc
+++ b/t/ogg.cc
@@ -1,6 +1,8 @@
 #include <opustags.h>
 #include "tap.h"
 
+#include <string.h>
+
 static void check_ref_ogg()
 {
 	ot::file input = fopen("gobble.opus", "r");
diff --git a/t/opus.cc b/t/opus.cc
index a575ee5..c185083 100644
--- a/t/opus.cc
+++ b/t/opus.cc
@@ -1,15 +1,7 @@
-/**
- * \file t/opus.cc
- *
- * Entry point of the unit test suite.
- * Follows the TAP protocol.
- *
- */
-
 #include <opustags.h>
 #include "tap.h"
 
-#include <cstring>
+#include <string.h>
 
 using namespace std::literals::string_literals;
 
diff --git a/t/tap.h b/t/tap.h
index bbef63a..709b4fa 100644
--- a/t/tap.h
+++ b/t/tap.h
@@ -5,6 +5,8 @@
  * Helpers for following the Test Anything Protocol.
  */
 
+#pragma once
+
 #include <exception>
 #include <iostream>