diff --git a/inc/winfsp/fsctl.h b/inc/winfsp/fsctl.h
index f2b083e6..24c63ef1 100644
--- a/inc/winfsp/fsctl.h
+++ b/inc/winfsp/fsctl.h
@@ -588,7 +588,7 @@ static inline FSP_FSCTL_TRANSACT_RSP *FspFsctlTransactConsumeResponse(
     return NextResponse <= ResponseBufEnd ? (FSP_FSCTL_TRANSACT_RSP *)NextResponse : 0;
 }
 
-#if !defined(WINFSP_SYS_INTERNAL)
+#if !defined(_KERNEL_MODE)
 FSP_API NTSTATUS FspFsctlCreateVolume(PWSTR DevicePath,
     const FSP_FSCTL_VOLUME_PARAMS *VolumeParams,
     PWCHAR VolumeNameBuf, SIZE_T VolumeNameSize,
diff --git a/opt/fsext/inc/winfsp/fsext.h b/opt/fsext/inc/winfsp/fsext.h
new file mode 100644
index 00000000..21bbe62a
--- /dev/null
+++ b/opt/fsext/inc/winfsp/fsext.h
@@ -0,0 +1,60 @@
+/**
+ * @file winfsp/fsext.h
+ *
+ * @copyright 2015-2019 Bill Zissimopoulos
+ */
+/*
+ * This file is part of WinFsp.
+ *
+ * You can redistribute it and/or modify it under the terms of the GNU
+ * General Public License version 3 as published by the Free Software
+ * Foundation.
+ *
+ * Licensees holding a valid commercial license may use this software
+ * in accordance with the commercial license agreement provided in
+ * conjunction with the software.  The terms and conditions of any such
+ * commercial license agreement shall govern, supersede, and render
+ * ineffective any application of the GPLv3 license to this software,
+ * notwithstanding of any reference thereto in the software or
+ * associated repository.
+ */
+
+#ifndef WINFSP_FSEXT_H_INCLUDED
+#define WINFSP_FSEXT_H_INCLUDED
+
+#if !defined(_KERNEL_MODE)
+#error This file can only be included when compiling for kernel mode.
+#endif
+
+#include <winfsp/fsctl.h>
+
+#if defined(WINFSP_SYS_INTERNAL)
+#define FSP_DDI                         __declspec(dllexport)
+#else
+#define FSP_DDI                         __declspec(dllimport)
+#endif
+#if !defined(FSP_DDI_DEF)
+#define FSP_DDI_DEF(RetType, Name, ...) FSP_DDI RetType NTAPI Name ( __VA_ARGS__ );
+#endif
+
+typedef struct
+{
+    UINT32 Version;
+    /* in */
+    UINT32 DeviceTransactCode;
+    UINT32 DeviceExtensionSize;
+    NTSTATUS (*DeviceInit)(PDEVICE_OBJECT DeviceObject);
+    VOID (*DeviceFini)(PDEVICE_OBJECT DeviceObject);
+    VOID (*DeviceExpirationRoutine)(PDEVICE_OBJECT DeviceObject, UINT64 ExpirationTime);
+    NTSTATUS (*DeviceTransact)(PIRP Irp, PDEVICE_OBJECT DeviceObject);
+    /* out */
+    UINT32 DeviceExtensionOffset;
+} FSP_FSEXT_PROVIDER;
+
+FSP_DDI_DEF(NTSTATUS, FspFsextRegisterProvider, FSP_FSEXT_PROVIDER *Provider)
+
+FSP_DDI_DEF(NTSTATUS, FspPosixMapSidToUid, PSID Sid, PUINT32 PUid)
+FSP_DDI_DEF(NTSTATUS, FspPosixMapWindowsToPosixPathEx, PWSTR WindowsPath, char **PPosixPath,
+    BOOLEAN Translate)
+
+#endif
diff --git a/opt/fsext/lib/winfsp-x64.lib b/opt/fsext/lib/winfsp-x64.lib
new file mode 100644
index 00000000..dfc37e8b
Binary files /dev/null and b/opt/fsext/lib/winfsp-x64.lib differ
diff --git a/opt/fsext/lib/winfsp-x86.lib b/opt/fsext/lib/winfsp-x86.lib
new file mode 100644
index 00000000..9e47ca09
Binary files /dev/null and b/opt/fsext/lib/winfsp-x86.lib differ
diff --git a/opt/fsext/lib/winfsp.impdef b/opt/fsext/lib/winfsp.impdef
new file mode 100644
index 00000000..de283148
--- /dev/null
+++ b/opt/fsext/lib/winfsp.impdef
@@ -0,0 +1,6 @@
+// tools\impdef.bat lib\winfsp.impdef lib\winfsp-x64.lib
+// tools\impdef.bat lib\winfsp.impdef lib\winfsp-x86.lib
+
+#define FSP_DDI_DEF(RetType, Name, ...) __declspec(dllexport) RetType NTAPI Name ( __VA_ARGS__ ) {}
+#include <ntifs.h>
+#include <winfsp/fsext.h>
diff --git a/tools/impdef.bat b/tools/impdef.bat
new file mode 100644
index 00000000..60e13df5
--- /dev/null
+++ b/tools/impdef.bat
@@ -0,0 +1,44 @@
+@echo off
+
+setlocal
+setlocal EnableDelayedExpansion
+
+if X%1==X goto usage
+if X%2==X goto usage
+set infile=%1
+set infile=%infile:/=\%
+set outfile=%2
+set outfile=%outfile:/=\%
+set workdir=!infile!.work
+set workbase=!workdir!\%~n1
+set outarch=%~n2
+set outarch=%outarch:~-3%
+
+set arch=x64
+set cdef=/D_AMD64_
+if /i X%outarch%==Xx86 set arch=x86
+if /i X%outarch%==Xx86 set cdef=/D_X86_
+
+call "%VS140COMNTOOLS%\..\..\VC\vcvarsall.bat" !arch!
+set INCLUDE=%~dp0..\opt\fsext\inc;%~dp0..\inc;!WindowsSdkDir!Include\!WindowsSDKVersion!km\crt;!WindowsSdkDir!Include\!WindowsSDKVersion!km;!WindowsSdkDir!Include\!WindowsSDKVersion!km\shared;!INCLUDE!
+
+if exist !workdir! rmdir /s/q !workdir!
+mkdir !workdir!
+
+type !infile! >>!workbase!.c
+cl /LD /Fe!workbase!.sys /Fo!workbase!.obj !cdef! /D_KERNEL_MODE /wd4716 !workbase!.c
+if errorlevel 1 goto fail
+
+copy !workbase!.lib !outfile!
+if errorlevel 1 goto fail
+
+rmdir /s/q !workdir!
+
+exit /b 0
+
+:fail
+exit /b 1
+
+:usage
+echo usage: impdef.bat infile.impdef outfile.lib 1>&2
+exit /b 2