wasm webassembly: creating opengl v 3 (webgl2) context fails

Using the contextinfo example app, creating an opengl 3 context fails:

(QHtml5OpenGLContext::makeCurrent:119) - virtual bool QHtml5OpenGLContext::makeCurrent(QPlatformSurface *) 43
qtloader.js:254:17
(Widget::start:296) - Requesting surface format QSurfaceFormat(version 3.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 16, redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1, stencilBufferSize -1, samples -1, swapBehavior QSurfaceFormat::SwapBehavior(DefaultSwapBehavior), swapInterval 1, colorSpace QSurfaceFormat::ColorSpace(DefaultColorSpace), profile QSurfaceFormat::OpenGLContextProfile(NoProfile))
qtloader.js:254:17
(QHtml5Window::QHtml5Window:56) - QHtml5Window 0xb472a0: 0x8532a0 0x3
qtloader.js:254:17
qtloader.js:254:17
(QHtml5Window::QHtml5Window:58) - Surfacetype 1
qtloader.js:254:17
(QHtml5OpenGLContext::createEmscriptenContext:82) - static EMSCRIPTEN_WEBGL_CONTEXT_HANDLE QHtml5OpenGLContext::createEmscriptenContext(const char *, QSurfaceFormat) 3
qtloader.js:254:17
Could not create canvas: ?,,

{"alpha":false,"depth":true,"stencil":false,"antialias":true,"premultipliedAlpha":true,"preserveDrawingBuffer":false,"preferLowPowerToHighPerformance":false,"failIfMajorPerformanceCaveat":false,"majorVersion":2,"minorVersion":0,"explicitSwapControl":0}