diff --git a/src/sys/dirctl.c b/src/sys/dirctl.c
index f3b65712..797f2cb1 100644
--- a/src/sys/dirctl.c
+++ b/src/sys/dirctl.c
@@ -172,7 +172,7 @@ static NTSTATUS FspFsvolQueryDirectoryCopy(
                 }
 
                 if (0 != PrevDestBuf)
-                    *(PULONG)PrevDestBuf = (ULONG)((PUINT8)DestBuf - DestBufBgn);
+                    *(PULONG)PrevDestBuf = (ULONG)((PUINT8)DestBuf - (PUINT8)PrevDestBuf);
                 PrevDestBuf = DestBuf;
 
                 *PDirectoryOffset = DirInfo->NextOffset;