1 files changed, 8 insertions, 1 deletions

diff --git a/web/callback.js b/web/callback.js
index 178b8e9..e277cf5 100644
--- a/web/callback.js
+++ b/web/callback.js
@@ -31,8 +31,15 @@ addCallbackFunction: function(f) {
 
 callFunction__deps: [ 'cbfl', 'validateCallbackId' ],
 callFunction: function(id, arg) {
+  // This is a workaround related to usign WASM64
+  // JavaScript's UTF8ToString expects a pointer argument, which for JS is
+  // of type "number", but WASM64 is passing a BigInt. See also:
+  // https://github.com/emscripten-core/emscripten/issues/21541
+  // (but I could not make the suggested solution work in this case).
+  // TODO: check if there is a better workaround.
+  const non64_arg = Number(arg);
   if (_validateCallbackId(id))
-    _cbfl[id](UTF8ToString(arg));
+    _cbfl[id](UTF8ToString(non64_arg));
 },
 
 callFunctionInt__deps: [ 'cbfl', 'validateCallbackId' ],