diff --git a/polyfill/lib/ecmascript.mjs b/polyfill/lib/ecmascript.mjs
index d1865acd9e..93eb82dc8f 100644
--- a/polyfill/lib/ecmascript.mjs
+++ b/polyfill/lib/ecmascript.mjs
@@ -1956,11 +1956,15 @@ export const ES = ObjectAssign({}, ES2022, {
     return result;
   },
 
+  ObjectImplementsTemporalTimeZoneProtocol: (object) => {
+    if (ES.IsTemporalTimeZone(object)) return true;
+    return 'getOffsetNanosecondsFor' in object && 'getPossibleInstantsFor' in object && 'id' in object;
+  },
   ToTemporalTimeZoneSlotValue: (temporalTimeZoneLike) => {
     if (ES.Type(temporalTimeZoneLike) === 'Object') {
       if (ES.IsTemporalZonedDateTime(temporalTimeZoneLike)) return GetSlot(temporalTimeZoneLike, TIME_ZONE);
-      if (ES.IsTemporalCalendar(temporalTimeZoneLike)) {
-        throw new RangeError('Expected a time zone object but received a Temporal.Calendar');
+      if (!ES.ObjectImplementsTemporalTimeZoneProtocol(temporalTimeZoneLike)) {
+        throw new TypeError('expected a Temporal.TimeZone or object implementing the Temporal.TimeZone protocol');
       }
       return temporalTimeZoneLike;
     }
diff --git a/spec/timezone.html b/spec/timezone.html
index ea4667f929..3b44f7d35f 100644
--- a/spec/timezone.html
+++ b/spec/timezone.html
@@ -546,6 +546,28 @@ <h1>FormatISOTimeZoneOffsetString ( _offsetNanoseconds_ )</h1>
       </emu-alg>
     </emu-clause>
 
+    <emu-clause id="sec-temporal-objectimplementstemporaltimezoneprotocol" type="abstract operation">
+      <h1>
+        ObjectImplementsTemporalTimeZoneProtocol (
+          _object_: an Object,
+        ): either a normal completion containing a Boolean, or a throw completion
+      </h1>
+      <dl class="header">
+        <dt>description</dt>
+        <dd>
+          It determines whether the given _object_ is a Temporal.TimeZone instance or implements the required methods from the Temporal.TimeZone protocol.
+          For ordinary objects, and some exotic objects, this operation is infallible and will always return a normal completion.
+          However, if _object_ is a Proxy or has one in its prototype chain, user code may be called.
+        </dd>
+      </dl>
+      <emu-alg>
+        1. If _object_ has an [[InitializedTemporalTimeZone]] internal slot, return *true*.
+        1. For each property key _key_ of « *"getOffsetNanosecondsFor"*, *"getPossibleInstantsFor"*, *"id"* », do
+          1. If ? HasProperty(_object_, _key_) is *false*, return *false*.
+        1. Return *true*.
+      </emu-alg>
+    </emu-clause>
+
     <emu-clause id="sec-temporal-totemporaltimezoneslotvalue" type="abstract operation">
       <h1>
         ToTemporalTimeZoneSlotValue (
@@ -560,7 +582,7 @@ <h1>
         1. If Type(_temporalTimeZoneLike_) is Object, then
           1. If _temporalTimeZoneLike_ has an [[InitializedTemporalZonedDateTime]] internal slot, then
             1. Return _temporalTimeZoneLike_.[[TimeZone]].
-          1. If _temporalTimeZoneLike_ has an [[InitializedTemporalCalendar]] internal slot, throw a *RangeError* exception.
+          1. If ? ObjectImplementsTemporalTimeZoneProtocol(_temporalTimeZoneLike_) is *false*, throw a *TypeError* exception.
           1. Return _temporalTimeZoneLike_.
         1. Let _identifier_ be ? ToString(_temporalTimeZoneLike_).
         1. Let _parseResult_ be ? ParseTemporalTimeZoneString(_identifier_).