diff --git a/spec.html b/spec.html
index 8af3c26d4cf..a6a85675c80 100644
--- a/spec.html
+++ b/spec.html
@@ -7756,6 +7756,7 @@
Static Semantics: IsFunctionDefinition
RelationalExpression `>=` ShiftExpression
RelationalExpression `instanceof` ShiftExpression
RelationalExpression `in` ShiftExpression
+ PrivateIdentifier `in` ShiftExpression
EqualityExpression :
EqualityExpression `==` RelationalExpression
@@ -8500,6 +8501,7 @@ Static Semantics: AssignmentTargetType
RelationalExpression `>=` ShiftExpression
RelationalExpression `instanceof` ShiftExpression
RelationalExpression `in` ShiftExpression
+ PrivateIdentifier `in` ShiftExpression
EqualityExpression :
EqualityExpression `==` RelationalExpression
@@ -17199,6 +17201,7 @@ Syntax
RelationalExpression[?In, ?Yield, ?Await] `>=` ShiftExpression[?Yield, ?Await]
RelationalExpression[?In, ?Yield, ?Await] `instanceof` ShiftExpression[?Yield, ?Await]
[+In] RelationalExpression[+In, ?Yield, ?Await] `in` ShiftExpression[?Yield, ?Await]
+ [+In] PrivateIdentifier `in` ShiftExpression[?Yield, ?Await]
The [In] grammar parameter is needed to avoid confusing the `in` operator in a relational expression with the `in` operator in a `for` statement.
@@ -17263,6 +17266,19 @@ Runtime Semantics: Evaluation
1. If Type(_rval_) is not Object, throw a *TypeError* exception.
1. Return ? HasProperty(_rval_, ? ToPropertyKey(_lval_)).
+ RelationalExpression : PrivateIdentifier `in` ShiftExpression
+
+ 1. Let _privateIdentifier_ be the StringValue of |PrivateIdentifier|.
+ 1. Let _rref_ be the result of evaluating |ShiftExpression|.
+ 1. Let _rval_ be ? GetValue(_rref_).
+ 1. If Type(_rval_) is not Object, throw a *TypeError* exception.
+ 1. Let _env_ be the running execution context's PrivateEnvironment.
+ 1. Let _privateNameBinding_ be ? ResolveBinding(_privateIdentifier_, _env_).
+ 1. Let _privateName_ be ? GetValue(_privateNameBinding_).
+ 1. Assert: _privateName_ is a Private Name.
+ 1. If ! PrivateElementFind(_privateName_, _rval) is not ~empty~, return *true*.
+ 1. Return *false*.
+
@@ -21305,6 +21321,14 @@ Static Semantics: AllPrivateIdentifiersValid
1. Append to _newNames_ the elements of PrivateBoundIdentifiers of |ClassBody|.
1. Return AllPrivateIdentifiersValid of |ClassElementList| with argument _newNames_.
+
+ RelationalExpression : PrivateIdentifier `in` ShiftExpression
+
+ 1. If StringValue of |PrivateIdentifier| is in _names_, return *true*.
+ 1. Return *false*.
+
+
+ For all other grammatical productions, recurse on subexpressions/substatements, passing in the _names_ of the caller. If all pieces return *true*, then return *true*. If any returns *false*, return *false*.
@@ -22170,6 +22194,7 @@ Expression Rules
RelationalExpression `>=` ShiftExpression
RelationalExpression `instanceof` ShiftExpression
RelationalExpression `in` ShiftExpression
+ PrivateIdentifier `in` ShiftExpression
ShiftExpression :
ShiftExpression `<<` AdditiveExpression