Magic header not detected (Webpack 4)

[budleigh]

Hi there - trying to integrate with a long-since-ejected CRA4 app. Using Webpack @4.44.2 and wasm-pack-plugin @1.6.0, my code (which amounts to literally the example code here) compiles correctly and I see the pkg output and have imported it into my normal JS code. I'm seeing a compilation error and a few additional errors in the browser amounting to:

• "the magic header is not present"
• "the .wasm file has the wrong mimetype (text)"
• "I probably need a different loader for the file"

I've tried using wasm-loader to no avail. Anyone encountered this or do I need to bite the bullet and bump to Webpack 5?