diff --git a/Meta/generate-libwasm-spec-test.py b/Meta/generate-libwasm-spec-test.py
index 7063449582d..08d83c76ca4 100644
--- a/Meta/generate-libwasm-spec-test.py
+++ b/Meta/generate-libwasm-spec-test.py
@@ -200,7 +200,7 @@ def make_description(input_path: Path, name: str, out_path: Path) -> WastDescrip
     return parse(description)
 
 
-def gen_value(value: WasmValue) -> str:
+def gen_value(value: WasmValue, as_arg=False) -> str:
     def unsigned_to_signed(uint: int, bits: int) -> int:
         max_value = 2**bits
         if uint >= 2 ** (bits - 1):
@@ -221,7 +221,13 @@ def gen_value(value: WasmValue) -> str:
         f = struct.unpack("d", b)[0]
         return f
 
-    def float_to_str(f: float) -> str:
+    def float_to_str(f: float, preserve_nan_sign=False) -> str:
+        if math.isnan(f) and preserve_nan_sign:
+            f_bytes = struct.pack("d", f)
+            # -NaN does not preserve the sign bit in JavaScript land, so if
+            # we want to preserve NaN "sign", we pass in raw bytes
+            return f"new Uint8Array({list(f_bytes)})"
+
         if math.isnan(f) and math.copysign(1.0, f) < 0:
             return "-NaN"
         elif math.isnan(f):
@@ -234,8 +240,6 @@ def gen_value(value: WasmValue) -> str:
 
     if value.value.startswith("nan"):
         return "NaN"
-    elif value.value.startswith("-nan"):
-        return "-NaN"
     elif value.value == "inf":
         return "Infinity"
     elif value.value == "-inf":
@@ -247,9 +251,9 @@ def gen_value(value: WasmValue) -> str:
         case "i64":
             return str(unsigned_to_signed(int(value.value), 64)) + "n"
         case "f32":
-            return float_to_str(int_to_float_bitcast(int(value.value)))
+            return float_to_str(int_to_float_bitcast(int(value.value)), as_arg)
         case "f64":
-            return float_to_str(int_to_float64_bitcast(int(value.value)))
+            return float_to_str(int_to_float64_bitcast(int(value.value)), as_arg)
         case "externref" | "funcref" | "v128":
             return value.value
         case _:
@@ -257,7 +261,7 @@ def gen_value(value: WasmValue) -> str:
 
 
 def gen_args(args: list[WasmValue]) -> str:
-    return ",".join(gen_value(arg) for arg in args)
+    return ",".join(gen_value(arg, True) for arg in args)
 
 
 def gen_module_command(command: ModuleCommand, ctx: Context):
diff --git a/Tests/LibWasm/test-wasm.cpp b/Tests/LibWasm/test-wasm.cpp
index 78c795b36c5..35459a91606 100644
--- a/Tests/LibWasm/test-wasm.cpp
+++ b/Tests/LibWasm/test-wasm.cpp
@@ -256,7 +256,17 @@ JS_DEFINE_NATIVE_FUNCTION(WebAssemblyModule::wasm_invoke)
     for (auto& param : type->parameters()) {
         auto argument = vm.argument(index++);
         double double_value = 0;
-        if (!argument.is_bigint())
+        if (argument.is_object()) {
+            auto object = MUST(argument.to_object(vm));
+            // Uint8Array allows for raw bytes to be passed into Wasm. This is
+            // particularly useful for preserving the sign bit of a NaN
+            if (!is<JS::Uint8Array>(*object))
+                return vm.throw_completion<JS::TypeError>("Expected a Uint8Array object"sv);
+            auto& array = static_cast<JS::Uint8Array&>(*object);
+            if (array.array_length().length() != 8)
+                return vm.throw_completion<JS::TypeError>("Expected a Uint8Array of size 8"sv);
+            memcpy(&double_value, array.data().data(), sizeof(double));
+        } else if (!argument.is_bigint())
             double_value = TRY(argument.to_double(vm));
         switch (param.kind()) {
         case Wasm::ValueType::Kind::I32: