System Javascript.lang context "template-string" causes error when referencing

After updating from Gtk+3 version 3.18.9 to 3.24.20 I found out that the syntax highlighting in my SourceView didn’t work properly for javascript code (other languages were ok).
In my custom markdown-extra2.lang I have the following syntax:

<context id="code-block-js" end-at-line-end="false" style-inside="true">
      <start>^```language-javascript[ \t]*$</start>

      	<context sub-pattern="0" where="start" style-ref="language-code-block"/>
      	<context sub-pattern="0" where="end" style-ref="language-code-block"/>
        <context ref="js:js"/>

I analyzed the diff (with Meld) between the two versions of the javascript.lang files and found that a new context with id template-string has been added. Commenting out that context definition solved the problem. So it’s not compatible with my code-block-js context.

Javascript.lang system file (/usr/share/…):

<context id="template-string" style-ref="string">
        <context id="template-expression" style-ref="function">

I I don’t comment out the template-string context in the javascript.lang file, then the end of my context (which is ```) is not recognized.

Can anyone tell me how to modify my context definition in order to play nicely along with the default javascript.lang file?