Error on roundtripping a testcase with "let"

[kripken]

(module
  (type $vector (array (field (mut f64))))
  (func $main
    (local $x i32)
    (local $y i32)
    (drop (local.get $x)) ;; 0 is the index appearing in the binary
    ;; first let
    (array.new_with_rtt $vector
      (f64.const 3.14159)
      (i32.const 1)
      (rtt.canon $vector)
    )
    (let (local $v (ref $vector))
      (drop (local.get $v)) ;; 0
      (drop (local.get $x)) ;; 1
      ;; another one, nested
      (array.new_with_rtt $vector
        (f64.const 1234)
        (i32.const 2)
        (rtt.canon $vector)
      )
      (let (local $w (ref $vector))
        (drop (local.get $v)) ;; 1
        (drop (local.get $w)) ;; 0
        (drop (local.get $x)) ;; 2
      )
    )
    ;; another one, later
    (array.new_with_rtt $vector
      (f64.const 2.1828)
      (i32.const 3)
      (rtt.canon $vector)
    )
    (let (local $v (ref $vector))
      (drop (local.get $v)) ;; 0
      (drop (local.get $x)) ;; 1
    )
    (drop (local.get $x)) ;; 0
  )
)

wat2wasm works, but running wasm2wat on the output hits

<unknown>:0000005d: Unexpected end instruction after 'end'
    2002 1a0b 0b44 9fab add8 5f76 01
              ^^                    

(testcase was written for WebAssembly/binaryen#3485)