diff --git a/ntoskrnl/io/iomgr/file.c b/ntoskrnl/io/iomgr/file.c
index 548c7f28db7..bfe11ab295b 100644
--- a/ntoskrnl/io/iomgr/file.c
+++ b/ntoskrnl/io/iomgr/file.c
@@ -857,7 +857,7 @@ IopParseDevice(IN PVOID ParseObject,
             }
 
             /* Clear the file object */
-            RtlZeroMemory(FileObject, sizeof(FILE_OBJECT));
+            RtlZeroMemory(FileObject, ObjectSize);
 
             /* Check if this is Synch I/O */
             if (OpenPacket->CreateOptions &
@@ -917,6 +917,7 @@ IopParseDevice(IN PVOID ParseObject,
                 /* Make sure the file object knows it has an extension */
                 FileObject->Flags |= FO_FILE_OBJECT_HAS_EXTENSION;
 
+                /* Initialize file object extension */
                 FileObjectExtension = (PFILE_OBJECT_EXTENSION)(FileObject + 1);
                 FileObject->FileObjectExtension = FileObjectExtension;