diff --git a/inc/winfsp/winfsp.h b/inc/winfsp/winfsp.h
index 09a630e8..1ead2dc9 100644
--- a/inc/winfsp/winfsp.h
+++ b/inc/winfsp/winfsp.h
@@ -115,9 +115,10 @@ typedef struct _FSP_FILE_SYSTEM_INTERFACE
 typedef struct _FSP_FILE_SYSTEM
 {
     UINT16 Version;
+    PVOID UserContext;
+    WCHAR VolumePrefix[sizeof(((FSP_FSCTL_VOLUME_PARAMS *)0)->Prefix) / sizeof(WCHAR)];
     WCHAR VolumeName[FSP_FSCTL_VOLUME_NAME_SIZEMAX / sizeof(WCHAR)];
     HANDLE VolumeHandle;
-    PVOID UserContext;
     FSP_FILE_SYSTEM_OPERATION_GUARD *EnterOperation, *LeaveOperation;
     FSP_FILE_SYSTEM_OPERATION *Operations[FspFsctlTransactKindCount];
     const FSP_FILE_SYSTEM_INTERFACE *Interface;
diff --git a/src/dll/dispatch.c b/src/dll/dispatch.c
index 1c341891..67dc2955 100644
--- a/src/dll/dispatch.c
+++ b/src/dll/dispatch.c
@@ -16,6 +16,29 @@ static FSP_FILE_SYSTEM_INTERFACE FspFileSystemNullInterface;
 static CRITICAL_SECTION FspFileSystemMountListGuard;
 static LIST_ENTRY FspFileSystemMountList = { &FspFileSystemMountList, &FspFileSystemMountList };
 
+static inline
+BOOL FspFileSystemDefineDosDevice(DWORD Flags, PWSTR MountPoint, FSP_FILE_SYSTEM *FileSystem)
+{
+    WCHAR TargetBuf[(
+        sizeof(((FSP_FILE_SYSTEM *)0)->VolumePrefix) +
+        sizeof(((FSP_FILE_SYSTEM *)0)->VolumeName)) / sizeof(WCHAR)];
+    PWSTR P;
+    ULONG L0, L1;
+
+    for (P = FileSystem->VolumeName; *P; P++)
+        ;
+    L0 = (ULONG)(P - FileSystem->VolumeName);
+    memcpy(TargetBuf, FileSystem->VolumeName, L0 * sizeof(WCHAR));
+
+    for (P = FileSystem->VolumePrefix; *P; P++)
+        ;
+    L1 = (ULONG)(P - FileSystem->VolumePrefix);
+    memcpy(TargetBuf + L0, FileSystem->VolumePrefix, L1 * sizeof(WCHAR));
+    TargetBuf[L0 + L1] = L'\0';
+
+    return DefineDosDeviceW(Flags, MountPoint, TargetBuf);
+}
+
 VOID FspFileSystemInitialize(VOID)
 {
     /*
@@ -62,8 +85,9 @@ VOID FspFileSystemFinalize(VOID)
     {
         FileSystem = CONTAINING_RECORD(MountEntry, FSP_FILE_SYSTEM, MountEntry);
 
-        DefineDosDeviceW(DDD_RAW_TARGET_PATH | DDD_REMOVE_DEFINITION | DDD_EXACT_MATCH_ON_REMOVE,
-            FileSystem->MountPoint, FileSystem->VolumeName);
+        FspFileSystemDefineDosDevice(
+            DDD_RAW_TARGET_PATH | DDD_REMOVE_DEFINITION | DDD_EXACT_MATCH_ON_REMOVE,
+            FileSystem->MountPoint, FileSystem);
     }
 
     LeaveCriticalSection(&FspFileSystemMountListGuard);
@@ -76,6 +100,7 @@ FSP_API NTSTATUS FspFileSystemCreate(PWSTR DevicePath,
 {
     NTSTATUS Result;
     FSP_FILE_SYSTEM *FileSystem;
+    ULONG PrefixLength;
 
     *PFileSystem = 0;
 
@@ -96,6 +121,14 @@ FSP_API NTSTATUS FspFileSystemCreate(PWSTR DevicePath,
         return Result;
     }
 
+    memcpy(FileSystem->VolumePrefix, VolumeParams->Prefix, sizeof VolumeParams->Prefix);
+    FileSystem->VolumePrefix[sizeof FileSystem->VolumePrefix / sizeof(WCHAR) - 1] = L'\0';
+    for (PrefixLength = 0; L'\0' != FileSystem->VolumePrefix[PrefixLength]; PrefixLength++)
+        ;
+    for (; 0 < PrefixLength && L'\\' == FileSystem->VolumePrefix[PrefixLength - 1]; PrefixLength--)
+        ;
+    FileSystem->VolumePrefix[PrefixLength] = L'\0';
+
     FileSystem->Operations[FspFsctlTransactCreateKind] = FspFileSystemOpCreate;
     FileSystem->Operations[FspFsctlTransactOverwriteKind] = FspFileSystemOpOverwrite;
     FileSystem->Operations[FspFsctlTransactCleanupKind] = FspFileSystemOpCleanup;
@@ -150,7 +183,7 @@ FSP_API NTSTATUS FspFileSystemSetMountPoint(FSP_FILE_SYSTEM *FileSystem, PWSTR M
                 if (0 == (Drives & (1 << (Drive - 'A'))))
                 {
                     MountPoint[0] = Drive;
-                    if (DefineDosDeviceW(DDD_RAW_TARGET_PATH, MountPoint, FileSystem->VolumeName))
+                    if (FspFileSystemDefineDosDevice(DDD_RAW_TARGET_PATH, MountPoint, FileSystem))
                     {
                         Result = STATUS_SUCCESS;
                         goto exit;
@@ -176,7 +209,7 @@ FSP_API NTSTATUS FspFileSystemSetMountPoint(FSP_FILE_SYSTEM *FileSystem, PWSTR M
         memcpy(P, MountPoint, L);
         MountPoint = P;
 
-        if (DefineDosDeviceW(DDD_RAW_TARGET_PATH, MountPoint, FileSystem->VolumeName))
+        if (FspFileSystemDefineDosDevice(DDD_RAW_TARGET_PATH, MountPoint, FileSystem))
             Result = STATUS_SUCCESS;
         else
             Result = FspNtStatusFromWin32(GetLastError());
@@ -206,8 +239,8 @@ FSP_API VOID FspFileSystemRemoveMountPoint(FSP_FILE_SYSTEM *FileSystem)
     RemoveEntryList(&FileSystem->MountEntry);
     LeaveCriticalSection(&FspFileSystemMountListGuard);
 
-    DefineDosDeviceW(DDD_RAW_TARGET_PATH | DDD_REMOVE_DEFINITION | DDD_EXACT_MATCH_ON_REMOVE,
-        FileSystem->MountPoint, FileSystem->VolumeName);
+    FspFileSystemDefineDosDevice(DDD_RAW_TARGET_PATH | DDD_REMOVE_DEFINITION | DDD_EXACT_MATCH_ON_REMOVE,
+        FileSystem->MountPoint, FileSystem);
 
     MemFree(FileSystem->MountPoint);
     FileSystem->MountPoint = 0;