diff --git a/src/embind/embind.js b/src/embind/embind.js
index d9035d788e5af..c6f8c4fa79488 100644
--- a/src/embind/embind.js
+++ b/src/embind/embind.js
@@ -642,11 +642,13 @@ var LibraryEmbind = {
             return value;
         },
         'toWireType': function(destructors, value) {
-            // todo: Here we have an opportunity for -O3 level "unsafe" optimizations: we could
-            // avoid the following if() and assume value is of proper type.
+#if ASSERTIONS
             if (typeof value !== "number" && typeof value !== "boolean") {
                 throw new TypeError('Cannot convert "' + _embind_repr(value) + '" to ' + this.name);
             }
+#endif
+            // The VM will perform JS to Wasm value conversion, according to the spec:
+            // https://www.w3.org/TR/wasm-js-api-1/#towebassemblyvalue
             return value;
         },
         'argPackAdvance': 8,