diff --git a/headers/os/kernel/OS.h b/headers/os/kernel/OS.h
index 7988385309..6c24064ae1 100644
--- a/headers/os/kernel/OS.h
+++ b/headers/os/kernel/OS.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2004-2009, Haiku Inc. All Rights Reserved.
+ * Copyright 2004-2019, Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  */
 #ifndef _OS_H
@@ -7,7 +7,7 @@
 
 /** Kernel specific structures and functions */
 
-#include <pthread.h>
+#include <sys/types.h>
 #include <stdarg.h>
 
 #include <SupportDefs.h>
diff --git a/src/apps/haikudepot/server/ServerSettings.cpp b/src/apps/haikudepot/server/ServerSettings.cpp
index 7a24a887d2..3d80bad790 100644
--- a/src/apps/haikudepot/server/ServerSettings.cpp
+++ b/src/apps/haikudepot/server/ServerSettings.cpp
@@ -7,6 +7,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <pthread.h>
 
 #include <AppFileInfo.h>
 #include <Application.h>
@@ -173,4 +174,4 @@ ServerSettings::SetClientTooOld()
 {
 	BAutolock locker(&sLock);
 	sClientTooOld = true;
-}
\ No newline at end of file
+}
diff --git a/src/apps/mail/QueryList.cpp b/src/apps/mail/QueryList.cpp
index 59d5624616..948a888e17 100644
--- a/src/apps/mail/QueryList.cpp
+++ b/src/apps/mail/QueryList.cpp
@@ -6,6 +6,8 @@
 
 #include "QueryList.h"
 
+#include <pthread.h>
+
 #include <Autolock.h>
 #include <Debug.h>
 #include <NodeMonitor.h>
diff --git a/src/kits/interface/ColorConversion.cpp b/src/kits/interface/ColorConversion.cpp
index 0f46f2ef47..71d92125c3 100644
--- a/src/kits/interface/ColorConversion.cpp
+++ b/src/kits/interface/ColorConversion.cpp
@@ -21,6 +21,7 @@
 
 #include <new>
 #include <string.h>
+#include <pthread.h>
 
 
 using std::nothrow;
diff --git a/src/kits/interface/Font.cpp b/src/kits/interface/Font.cpp
index 5e65bbc695..6c34c014be 100644
--- a/src/kits/interface/Font.cpp
+++ b/src/kits/interface/Font.cpp
@@ -30,6 +30,8 @@
 #include <new>
 #include <stdio.h>
 #include <stdlib.h>
+#include <pthread.h>
+
 
 using namespace std;
 
diff --git a/src/kits/storage/disk_device/DiskSystemAddOnManager.cpp b/src/kits/storage/disk_device/DiskSystemAddOnManager.cpp
index d55bdbb439..31fa10df9b 100644
--- a/src/kits/storage/disk_device/DiskSystemAddOnManager.cpp
+++ b/src/kits/storage/disk_device/DiskSystemAddOnManager.cpp
@@ -11,6 +11,7 @@
 #include <string>
 
 #include <stdio.h>
+#include <pthread.h>
 
 #include <Directory.h>
 #include <Entry.h>
diff --git a/src/system/libroot/posix/semaphore.cpp b/src/system/libroot/posix/semaphore.cpp
index 4df5a526aa..394e6b0898 100644
--- a/src/system/libroot/posix/semaphore.cpp
+++ b/src/system/libroot/posix/semaphore.cpp
@@ -10,6 +10,7 @@
 #include <fcntl.h>
 #include <stdarg.h>
 #include <stdlib.h>
+#include <pthread.h>
 
 #include <OS.h>
 
diff --git a/src/system/libroot/posix/sys/mman.cpp b/src/system/libroot/posix/sys/mman.cpp
index 2f1122b83c..53ec383990 100644
--- a/src/system/libroot/posix/sys/mman.cpp
+++ b/src/system/libroot/posix/sys/mman.cpp
@@ -9,6 +9,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
+#include <pthread.h>
 
 #include <OS.h>
 
diff --git a/src/system/libroot/posix/sys/xsi_msg_queue.cpp b/src/system/libroot/posix/sys/xsi_msg_queue.cpp
index 910523c0b2..9cafe13867 100644
--- a/src/system/libroot/posix/sys/xsi_msg_queue.cpp
+++ b/src/system/libroot/posix/sys/xsi_msg_queue.cpp
@@ -12,6 +12,7 @@
 #include <fcntl.h>
 #include <stdarg.h>
 #include <stdlib.h>
+#include <pthread.h>
 
 #include <OS.h>