TeXmacs Maxima Integrals

I've been trying to get TeXmacs with its Maxima plugin to work.

Enabling the "mathematical input" mode in its interactive sessions I can use TeXmacs as a nice computer algebra system. However, an issue arises when I use integration.

If I enter \(\displaystyle\int x\,\mathrm{d}\,x\) with "\int <enter>x d<tab><tab>x" (spaces here are actually typed in while the "<tab>"s and "<enter>"s are their respective keys), I get this idiosyncratic error:

incorrect syntax: 1 is not an infix operator
integrate( x 1,
	     ^

This seems to be a bug when TeXmacs is translating things into Maxima. Just replace the "<tab>" between the integrand and the "\(\mathrm{d}\)" with a multiplication operator entered by "*". For example, \int <enter>x*d<tab><tab>x yields the correct result of \(\displaystyle\frac{x^2}{2}\) rather than the nonsensical error.

For reference, the source code of a demonstration document is included below in Scheme and XML-like (?) formats.

(document (TeXmacs "2.1.1") (style (tuple "generic" "maxima")) (body (document (session "maxima" "default" (document (unfolded-io-math (document (with "color" "red" (concat "(" (with "math-font-family" "rm" "%i") "8) "))) (document (concat (big "int") " x  x")) (document "" "incorrect syntax: 1 is not an infix operator" "integrate( x 1," "             ^")) (unfolded-io-math (document (with "color" "red" (concat "(" (with "math-font-family" "rm" "%i") "8) "))) (document (concat (big "int") "x* x")) (document "" (concat " " (math (with "math-display" "true" (concat (text (with "font-family" "tt" "color" "red" (concat "(" (with "math-font-family" "rm" "%o8") ") "))) (frac (concat "x" (rsup "2")) "2"))))))))))) (initial (collection (associate "page-medium" "paper") (associate "preamble" "true") (associate "prog-scripts" "maxima"))))

<TeXmacs|2.1.1>

<style|<tuple|generic|maxima>>

<\body>
  <\session|maxima|default>
    <\unfolded-io-math>
      <with|color|red|(<with|math-font-family|rm|%i>8) >
    <|unfolded-io-math>
      <big|int> x \<mathd\> x
    <|unfolded-io-math>
      \;

      incorrect syntax: 1 is not an infix operator

      integrate( x 1,

      \ \ \ \ \ \ \ \ \ \ \ \ \ ^
    </unfolded-io-math>

    <\unfolded-io-math>
      <with|color|red|(<with|math-font-family|rm|%i>8) >
    <|unfolded-io-math>
      <big|int>x*\<mathd\> x
    <|unfolded-io-math>
      \;

      \ <math|<with|math-display|true|<text|<with|font-family|tt|color|red|(<with|math-font-family|rm|%o8>)
      >><frac|x<rsup|2>|2>>>
    </unfolded-io-math>
  </session>
</body>

<\initial>
  <\collection>
    <associate|page-medium|paper>
    <associate|preamble|false>
    <associate|prog-scripts|maxima>
  </collection>
</initial>