diff --git a/pkg/fs/debug.go b/pkg/fs/debug.go
index 0548ff26d..d38774371 100644
--- a/pkg/fs/debug.go
+++ b/pkg/fs/debug.go
@@ -89,6 +89,12 @@ func (s *stat) Attr() fuse.Attr {
 	}
 }
 
+func (s *stat) Open(req *fuse.OpenRequest, res *fuse.OpenResponse, intr fs.Intr) (fs.Handle, fuse.Error) {
+	// Set DirectIO to keep this file from being cached in OS X's kernel.
+	res.Flags |= fuse.OpenDirectIO
+	return s, nil
+}
+
 func (s *stat) Read(req *fuse.ReadRequest, res *fuse.ReadResponse, intr fs.Intr) fuse.Error {
 	c := s.content()
 	if req.Offset > int64(len(c)) {
diff --git a/pkg/fs/mut.go b/pkg/fs/mut.go
index 5eafa51d3..97197f0b8 100644
--- a/pkg/fs/mut.go
+++ b/pkg/fs/mut.go
@@ -296,7 +296,7 @@ func (n *mutDir) Lookup(name string, intr fs.Intr) (ret fs.Node, err fuse.Error)
 //    foi->flags = O_CREAT | O_RDWR;
 //
 // 2013/07/21 05:26:35 <- &{Create [ID=0x3 Node=0x8 Uid=61652 Gid=5000 Pid=13115] "x" fl=514 mode=-rw-r--r-- fuse.Intr}
-// 2013/07/21 05:26:36 -> 0x3 Create {LookupResponse:{Node:23 Generation:0 EntryValid:1m0s AttrValid:1m0s Attr:{Inode:15976986887557313215 Size:0 Blocks:0 Atime:2013-07-21 05:23:51.537251251 +1200 NZST Mtime:2013-07-21 05:23:51.537251251 +1200 NZST Ctime:2013-07-21 05:23:51.537251251 +1200 NZST Crtime:2013-07-21 05:23:51.537251251 +1200 NZST Mode:-rw------- Nlink:1 Uid:61652 Gid:5000 Rdev:0 Flags:0}} OpenResponse:{Handle:1 Flags:OpenDirectIO}}
+// 2013/07/21 05:26:36 -> 0x3 Create {LookupResponse:{Node:23 Generation:0 EntryValid:1m0s AttrValid:1m0s Attr:{Inode:15976986887557313215 Size:0 Blocks:0 Atime:2013-07-21 05:23:51.537251251 +1200 NZST Mtime:2013-07-21 05:23:51.537251251 +1200 NZST Ctime:2013-07-21 05:23:51.537251251 +1200 NZST Crtime:2013-07-21 05:23:51.537251251 +1200 NZST Mode:-rw------- Nlink:1 Uid:61652 Gid:5000 Rdev:0 Flags:0}} OpenResponse:{Handle:1 Flags:0}}
 func (n *mutDir) Create(req *fuse.CreateRequest, res *fuse.CreateResponse, intr fs.Intr) (fs.Node, fs.Handle, fuse.Error) {
 	child, err := n.creat(req.Name, fileType)
 	if err != nil {
@@ -310,11 +310,6 @@ func (n *mutDir) Create(req *fuse.CreateRequest, res *fuse.CreateResponse, intr
 		return nil, nil, ferr
 	}
 
-	// This isn't required (or even ever been shown to make a
-	// difference), but we do it to match OpenRequest below, where
-	// it causes test failures without:
-	res.OpenResponse.Flags &= ^fuse.OpenDirectIO
-
 	return child, h, nil
 }
 
@@ -681,10 +676,6 @@ func (n *mutFile) Open(req *fuse.OpenRequest, res *fuse.OpenResponse, intr fs.In
 		return nil, fuse.EIO
 	}
 
-	// Turn off the OpenDirectIO bit (on by default in rsc fuse server.go),
-	// else append operations don't work for some reason.
-	res.Flags &= ^fuse.OpenDirectIO
-
 	// Read-only.
 	if !isWriteFlags(req.Flags) {
 		mutFileOpenRO.Incr()