diff --git a/extra/io/monitor/monitor.factor b/extra/io/monitor/monitor.factor
index 4dc5081513..fe33045e01 100755
--- a/extra/io/monitor/monitor.factor
+++ b/extra/io/monitor/monitor.factor
@@ -1,11 +1,39 @@
 ! Copyright (C) 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: io.backend kernel continuations ;
+USING: io.backend kernel continuations namespaces sequences
+assocs hashtables sorting arrays ;
 IN: io.monitor
 
+<PRIVATE
+
+TUPLE: monitor queue closed? ;
+
+: check-monitor ( monitor -- )
+    monitor-closed? [ "Monitor closed" throw ] when ;
+
+: (monitor) ( delegate -- monitor )
+    H{ } clone {
+        set-delegate
+        set-monitor-queue
+    } monitor construct ;
+
+HOOK: fill-queue io-backend ( monitor -- assoc )
+
+: changed-file ( changed path -- )
+    namespace [ swap add ] change-at ;
+
+: dequeue-change ( assoc -- path changes )
+    delete-any prune natural-sort >array ;
+
+PRIVATE>
+
 HOOK: <monitor> io-backend ( path recursive? -- monitor )
 
-HOOK: next-change io-backend ( monitor -- path changes )
+: next-change ( monitor -- path changed )
+    dup check-monitor
+    dup monitor-queue dup assoc-empty? [
+        drop dup fill-queue over set-monitor-queue next-change
+    ] [ nip dequeue-change ] if ;
 
 SYMBOL: +add-file+
 SYMBOL: +remove-file+
diff --git a/extra/io/unix/backend/backend.factor b/extra/io/unix/backend/backend.factor
index 1b66c0332e..7112c48551 100755
--- a/extra/io/unix/backend/backend.factor
+++ b/extra/io/unix/backend/backend.factor
@@ -14,9 +14,9 @@ TUPLE: io-task port callbacks ;
 
 : io-task-fd io-task-port port-handle ;
 
-: <io-task> ( port continuation class -- task )
-    >r 1vector io-task construct-boa r> construct-delegate ;
-    inline
+: <io-task> ( port continuation/f class -- task )
+    >r [ 1vector ] [ V{ } clone ] if* io-task construct-boa
+    r> construct-delegate ; inline
 
 TUPLE: input-task ;
 
@@ -194,7 +194,7 @@ TUPLE: mx-port mx ;
 TUPLE: mx-task ;
 
 : <mx-task> ( port -- task )
-    f io-task construct-boa mx-task construct-delegate ;
+    f mx-task <io-task> ;
 
 M: mx-task do-io-task
     io-task-port mx-port-mx 0 swap wait-for-events f ;
diff --git a/extra/io/windows/nt/monitor/monitor.factor b/extra/io/windows/nt/monitor/monitor.factor
index 8e0e63923d..1be91263c4 100755
--- a/extra/io/windows/nt/monitor/monitor.factor
+++ b/extra/io/windows/nt/monitor/monitor.factor
@@ -3,12 +3,10 @@
 USING: alien.c-types destructors io.windows
 io.windows.nt.backend kernel math windows windows.kernel32
 windows.types libc assocs alien namespaces continuations
-io.monitor io.nonblocking io.buffers io.files io sequences
-hashtables sorting arrays combinators ;
+io.monitor io.monitor.private io.nonblocking io.buffers io.files
+io sequences hashtables sorting arrays combinators ;
 IN: io.windows.nt.monitor
 
-TUPLE: monitor path recursive? queue closed? ;
-
 : open-directory ( path -- handle )
     FILE_LIST_DIRECTORY
     share-mode
@@ -22,23 +20,26 @@ TUPLE: monitor path recursive? queue closed? ;
     dup add-completion
     f <win32-file> ;
 
+TUPLE: win32-monitor path recursive? ;
+
+: <win32-monitor> ( path recursive? port -- monitor )
+    (monitor) {
+        set-win32-monitor-path
+        set-win32-monitor-recursive?
+        set-delegate
+    } win32-monitor construct ;
+
 M: windows-nt-io <monitor> ( path recursive? -- monitor )
     [
-        >r dup open-directory monitor <buffered-port> r> {
-            set-monitor-path
-            set-delegate
-            set-monitor-recursive?
-        } monitor construct
+        over open-directory win32-monitor <buffered-port>
+        <win32-monitor>
     ] with-destructors ;
 
-: check-closed ( monitor -- )
-    port-type closed eq? [ "Monitor closed" throw ] when ;
-
 : begin-reading-changes ( monitor -- overlapped )
     dup port-handle win32-file-handle
     over buffer-ptr
     pick buffer-size
-    roll monitor-recursive? 1 0 ?
+    roll win32-monitor-recursive? 1 0 ?
     FILE_NOTIFY_CHANGE_ALL
     0 <uint>
     (make-overlapped)
@@ -49,6 +50,7 @@ M: windows-nt-io <monitor> ( path recursive? -- monitor )
         [
             dup begin-reading-changes
             swap [ save-callback ] 2keep
+            dup check-monitor ! we may have closed it...
             get-overlapped-result
         ] with-port-timeout
     ] with-destructors ;
@@ -63,7 +65,7 @@ M: windows-nt-io <monitor> ( path recursive? -- monitor )
         { [ t ] [ +modify-file+ ] }
     } cond nip ;
 
-: changed-file ( directory buffer -- changed path )
+: parse-file-notify ( directory buffer -- changed path )
     {
         FILE_NOTIFY_INFORMATION-FileName
         FILE_NOTIFY_INFORMATION-FileNameLength
@@ -71,22 +73,10 @@ M: windows-nt-io <monitor> ( path recursive? -- monitor )
     } get-slots >r memory>u16-string path+ r> parse-action swap ;
 
 : (changed-files) ( directory buffer -- )
-    2dup changed-file namespace [ swap add ] change-at
+    2dup parse-file-notify changed-file
     dup FILE_NOTIFY_INFORMATION-NextEntryOffset dup zero?
     [ 3drop ] [ swap <displaced-alien> (changed-files) ] if ;
 
-: changed-files ( directory buffer len -- assoc )
+M: windows-nt-io fill-queue ( monitor -- assoc )
+    dup win32-monitor-path over buffer-ptr rot read-changes
     [ zero? [ 2drop ] [ (changed-files) ] if ] H{ } make-assoc ;
-
-: fill-queue ( monitor -- )
-    dup monitor-path over buffer-ptr pick read-changes
-    changed-files
-    swap set-monitor-queue ;
-
-M: windows-nt-io next-change ( monitor -- path changes )
-    dup check-closed
-    dup monitor-queue dup assoc-empty? [
-        drop dup fill-queue next-change
-    ] [
-        nip delete-any prune natural-sort >array
-    ] if ;