diff --git a/Libs/Hopac/Stream.fs b/Libs/Hopac/Stream.fs
index f69608a5..aac2cbf0 100644
--- a/Libs/Hopac/Stream.fs
+++ b/Libs/Hopac/Stream.fs
@@ -281,24 +281,20 @@ module Stream =
 
   let ambAll (xxs: Stream<#Stream<_>>) = joinWith amb' xxs
 
-  let rec mergeAll' (streams: Stream<'x> option) (producer: Stream<Stream<'x>> option) : Stream<'x> =
-    match streams, producer with
-    | None, Some p ->
-        p ^=> function Nil -> mergeAll' None None
-                     | Cons (x, xs) -> mergeAll' (Some x) (Some xs)
-        |> memo
-    | Some s, None ->
-        s ^=> function Cons (x, xs) -> consj x (mergeAll' (Some xs) producer)
-                     | Nil -> mergeAll' None producer :> _
-        |> memo
-    | Some s, Some p ->
-        Alt.choose [ s ^=> function Cons (x, xs) -> consj x (mergeAll' (Some xs) producer)
-                                  | Nil -> mergeAll' None producer :> _
-                     p ^=> function Cons (x, xs) -> mergeAll' (merge s x |> Some) (Some xs)
-                                    | Nil -> mergeAll' streams None ] |> memo
-    | None, None -> memo nilj
-
-  let mergeAll producer = mergeAll' None (Some producer)
+  let rec mergeAll' (combined: Stream<'x>) (producer: Stream<Stream<'x>>) : Stream<'x> =
+    combined ^=> function
+      | Nil -> producer >>= function
+        | Nil -> nilj
+        | Cons (x, xs) -> mergeAll' x xs :> _
+      | Cons (v, vs) -> consj v (mergeAll' vs producer)
+    <|> producer ^=> function
+      | Nil -> combined >>= function
+        | Nil -> nilj
+        | Cons (v, vs) -> consj v (mergeAll' vs nil)
+      | Cons (x, xs) -> mergeAll' (merge combined x) xs :> _
+    |> memo
+
+  let mergeAll producer = mergeAll' nil producer
     
 
   let appendAll (xxs: Stream<#Stream<_>>) = joinWith append' xxs