diff --git a/spec.html b/spec.html
index bdb0fd9555..1a9cf8bd07 100644
--- a/spec.html
+++ b/spec.html
@@ -19028,7 +19028,7 @@ <h1>Runtime Semantics: ClassDefinitionEvaluation</h1>
         1. Let _constructorInfo_ be the result of performing DefineMethod for _constructor_ with arguments _proto_ and _constructorParent_ as the optional _functionPrototype_ argument.
         1. Assert: _constructorInfo_ is not an abrupt completion.
         1. Let _F_ be _constructorInfo_.[[Closure]].
-        1. If |ClassHeritage_opt| is present, set _F_'s [[ConstructorKind]] internal slot to `"derived"`.
+        1. If |ClassHeritage_opt| is present and _protoParent_ is not *null*, then set _F_'s [[ConstructorKind]] internal slot to `"derived"`.
         1. Perform MakeConstructor(_F_, *false*, _proto_).
         1. Perform MakeClassConstructor(_F_).
         1. Perform CreateMethodProperty(_proto_, `"constructor"`, _F_).