diff --git a/headers/private/kernel/boot_device.h b/headers/private/kernel/boot_device.h
new file mode 100644
index 0000000000..915a08d715
--- /dev/null
+++ b/headers/private/kernel/boot_device.h
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2005, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _KERNEL_BOOT_DEVICE_H
+#define _KERNEL_BOOT_DEVICE_H
+
+
+#include <sys/types.h>
+
+
+extern dev_t gBootDevice;
+	// defined in fs/vfs_boot.cpp
+
+#endif	/* _KERNEL_BOOT_DEVICE_H */
diff --git a/src/system/kernel/device_manager/probe.cpp b/src/system/kernel/device_manager/probe.cpp
index b8aa8ff5ea..f59e54de62 100644
--- a/src/system/kernel/device_manager/probe.cpp
+++ b/src/system/kernel/device_manager/probe.cpp
@@ -15,8 +15,7 @@
 
 #include "device_manager_private.h"
 
-#include <KernelExport.h>
-#include <image.h>
+#include <boot_device.h>
 #include <elf.h>
 #include <kmodule.h>
 #include <fs/KPath.h>
@@ -24,6 +23,9 @@
 #include <util/Stack.h>
 #include <util/kernel_cpp.h>
 
+#include <image.h>
+#include <KernelExport.h>
+
 #include <stdlib.h>
 #include <dirent.h>
 #include <stdio.h>
@@ -70,8 +72,6 @@ static const char *kModulePaths[] = {
 	NULL
 };
 
-extern dev_t gBootDevice;
-	// from fs/vfs.cpp
 
 class DirectoryIterator {
 	public:
diff --git a/src/system/kernel/fs/devfs.cpp b/src/system/kernel/fs/devfs.cpp
index dbe43c29b4..0097a5df7d 100644
--- a/src/system/kernel/fs/devfs.cpp
+++ b/src/system/kernel/fs/devfs.cpp
@@ -14,6 +14,7 @@
 #include <pnp_devfs.h>
 #include <NodeMonitor.h>
 
+#include <boot_device.h>
 #include <kdevice_manager.h>
 #include <KPath.h>
 #include <vfs.h>
@@ -136,9 +137,6 @@ static status_t publish_device(struct devfs *fs, const char *path,
 					driver_entry *driver, device_hooks *ops);
 
 
-// The boot device, if already present
-extern dev_t gBootDevice;
-
 /* the one and only allowed devfs instance */
 static struct devfs *sDeviceFileSystem = NULL;
 
diff --git a/src/system/kernel/module.c b/src/system/kernel/module.c
index 967de4fabc..3d6e9ca4f6 100644
--- a/src/system/kernel/module.c
+++ b/src/system/kernel/module.c
@@ -11,17 +11,18 @@
  */
 
 
+#include <boot_device.h>
+#include <elf.h>
 #include <kmodule.h>
 #include <lock.h>
-#include <elf.h>
-#include <vfs.h>
 #include <util/khash.h>
+#include <vfs.h>
 #include <boot/elf.h>
 
-#include <sys/stat.h>
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
-#include <errno.h>
+#include <sys/stat.h>
 
 
 //#define TRACE_MODULE
@@ -160,8 +161,6 @@ static const char * const sModulePaths[] = {
 static hash_table *sModuleImagesHash;
 static hash_table *sModulesHash;
 
-extern dev_t gBootDevice;
-
 
 /** calculates hash for a module using its name */