diff --git a/spec.html b/spec.html
index 2c10ac3217..58ce385cde 100644
--- a/spec.html
+++ b/spec.html
@@ -49546,8 +49546,11 @@ <h1>
           </dl>
           <emu-alg>
             1. If IsPromise(_x_) is *true*, then
-              1. Let _xConstructor_ be ? Get(_x_, *"constructor"*).
-              1. If SameValue(_xConstructor_, _C_) is *true*, return _x_.
+              1. Assert: _x_ is an ordinary object.
+              1. Let _xProto_ be ! _x_.[[GetPrototypeOf]]().
+              1. Let _CPrototype_ be ? Get(_C_, *"prototype"*).
+              1. NOTE: When _C_ is the intrinsic %Promise%, the above step cannot throw and always results in the intrinsic %Promise.prototype%.
+              1. If SameValue(_xProto_, _CPrototype_) is *true*, return _x_.
             1. Let _promiseCapability_ be ? NewPromiseCapability(_C_).
             1. Perform ? Call(_promiseCapability_.[[Resolve]], *undefined*, « _x_ »).
             1. Return _promiseCapability_.[[Promise]].