wasm: declarative apps crash with threads

When I configure qtbase with webassembly threads and run an example such as quickcontrols2 gallery, Ithe app fails to run with:

Module.instantiateWasm callback failed with error: out of memory

 
worker.js onmessage() captured an uncaught exception: TypeError: can't access property "emscripten_stack_init", Module.asm is undefined gallery_controls2.worker.js:60:11
 
createQtAppInstance</</Module._emscripten_stack_init@blob:http://192.168.1.2:8000/7638253d-86e2-48d2-b503-9919ce1cd211:15505:3 stackCheckInit@blob:http://192.168.1.2:8000/7638253d-86e2-48d2-b503-9919ce1cd211:16315:3 run@blob:http://192.168.1.2:8000/7638253d-86e2-48d2-b503-9919ce1cd211:16327:3 createQtAppInstance</<@blob:http://192.168.1.2:8000/7638253d-86e2-48d2-b503-9919ce1cd211:16488:1 self.onmessage@http://192.168.1.2:8000/gallery_controls2.worker.js:108:26