diff --git a/cmake/QtWasmHelpers.cmake b/cmake/QtWasmHelpers.cmake
index 77c77d2882..5e09feac29 100644
--- a/cmake/QtWasmHelpers.cmake
+++ b/cmake/QtWasmHelpers.cmake
@@ -7,7 +7,8 @@ function (qt_internal_setup_wasm_target_properties wasmTarget)
     "SHELL:-s EXPORTED_RUNTIME_METHODS=[UTF16ToString,stringToUTF16,specialHTMLTargets]"
     "SHELL:-s USE_WEBGL2=1"
     "--bind"
-    "SHELL:-s FETCH=1")
+    "SHELL:-s FETCH=1"
+    "SHELL:-s WASM_BIGINT=1")
 
     # Enable MODULARIZE and set EXPORT_NAME, which makes it possible to
     # create application instances using a global constructor function,
diff --git a/mkspecs/wasm-emscripten/qmake.conf b/mkspecs/wasm-emscripten/qmake.conf
index 270ab39559..140f2b4801 100644
--- a/mkspecs/wasm-emscripten/qmake.conf
+++ b/mkspecs/wasm-emscripten/qmake.conf
@@ -38,7 +38,8 @@ EMCC_COMMON_LFLAGS += \
     --bind \
     -s FETCH=1 \
     -s MODULARIZE=1 \
-    -s EXPORT_NAME=createQtAppInstance
+    -s EXPORT_NAME=createQtAppInstance \
+    -s WASM_BIGINT=1
 
 # The -s arguments can also be used with release builds,
 # but are here in debug for clarity.