Index: /trunk/src/VBox/VMM/PDMAsyncCompletionFile.cpp
===================================================================
--- /trunk/src/VBox/VMM/PDMAsyncCompletionFile.cpp	(revision 27494)
+++ /trunk/src/VBox/VMM/PDMAsyncCompletionFile.cpp	(revision 27495)
@@ -779,4 +779,7 @@
                          ? RTFILE_O_READ      | RTFILE_O_OPEN | RTFILE_O_DENY_NONE
                          : RTFILE_O_READWRITE | RTFILE_O_OPEN | RTFILE_O_DENY_WRITE;
+
+    if (enmMgrType == PDMACEPFILEMGRTYPE_ASYNC)
+        fFileFlags |= RTFILE_O_ASYNC_IO;
 
     if (enmEpBackend == PDMACFILEEPBACKEND_NON_BUFFERED)