diff --git a/reactos/ntoskrnl/io/iomgr/irp.c b/reactos/ntoskrnl/io/iomgr/irp.c
index 0863f58907b..30107c16949 100644
--- a/reactos/ntoskrnl/io/iomgr/irp.c
+++ b/reactos/ntoskrnl/io/iomgr/irp.c
@@ -966,9 +966,12 @@ IoBuildSynchronousFsdRequest(IN ULONG MajorFunction,
                                         IoStatusBlock );
     if (!Irp) return NULL;
 
-    /* Set the Event which makes it Syncronous */
+    /* Associate the caller's event object with this IRP */
     Irp->UserEvent = Event;
 
+    /* Set the synchronous flag */
+    Irp->Flags |= IRP_SYNCHRONOUS_API;
+
     /* Sync IRPs are queued to requestor thread's irp cancel/cleanup list */
     IoQueueThreadIrp(Irp);
     return Irp;