diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
index 1e0e76b025..ea415d8619 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
@@ -117,7 +117,7 @@ Value get_option(GlobalObject& global_object, Object& options, String const& pro
 }
 
 // 13.8 ToTemporalRoundingMode ( normalizedOptions, fallback ), https://tc39.es/proposal-temporal/#sec-temporal-totemporalroundingmode
-String to_temporal_rounding_mode(GlobalObject& global_object, Object& normalized_options, String const& fallback)
+Optional<String> to_temporal_rounding_mode(GlobalObject& global_object, Object& normalized_options, String const& fallback)
 {
     auto& vm = global_object.vm();
 
@@ -424,7 +424,7 @@ Optional<TemporalInstant> parse_temporal_instant_string(GlobalObject& global_obj
 }
 
 // 13.37 ParseTemporalCalendarString ( isoString ), https://tc39.es/proposal-temporal/#sec-temporal-parsetemporalcalendarstring
-String parse_temporal_calendar_string([[maybe_unused]] GlobalObject& global_object, [[maybe_unused]] String const& iso_string)
+Optional<String> parse_temporal_calendar_string([[maybe_unused]] GlobalObject& global_object, [[maybe_unused]] String const& iso_string)
 {
     // 1. Assert: Type(isoString) is String.
 
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h b/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h
index d7667ce951..c0479427be 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.h
@@ -54,13 +54,13 @@ struct TemporalTimeZone {
 
 Object* get_options_object(GlobalObject&, Value options);
 Value get_option(GlobalObject&, Object& options, String const& property, Vector<OptionType> const& types, Vector<StringView> const& values, Value fallback);
-String to_temporal_rounding_mode(GlobalObject&, Object& normalized_options, String const& fallback);
+Optional<String> to_temporal_rounding_mode(GlobalObject&, Object& normalized_options, String const& fallback);
 u64 to_temporal_rounding_increment(GlobalObject&, Object& normalized_options, Optional<double> dividend, bool inclusive);
 Optional<String> to_smallest_temporal_unit(GlobalObject&, Object& normalized_options, Vector<StringView> const& disallowed_units, Optional<String> fallback);
 BigInt* round_number_to_increment(GlobalObject&, BigInt const&, u64 increment, String const& rounding_mode);
 Optional<ISODateTime> parse_iso_date_time(GlobalObject&, String const& iso_string);
 Optional<TemporalInstant> parse_temporal_instant_string(GlobalObject&, String const& iso_string);
-String parse_temporal_calendar_string(GlobalObject&, String const& iso_string);
+Optional<String> parse_temporal_calendar_string(GlobalObject&, String const& iso_string);
 Optional<TemporalDuration> parse_temporal_duration_string(GlobalObject&, String const& iso_string);
 Optional<TemporalTimeZone> parse_temporal_time_zone_string(GlobalObject&, String const& iso_string);
 
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
index f839eedd64..72270e198d 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
@@ -126,9 +126,10 @@ Object* to_temporal_calendar(GlobalObject& global_object, Value temporal_calenda
     // 3. If ! IsBuiltinCalendar(identifier) is false, then
     if (!is_builtin_calendar(identifier)) {
         // a. Let identifier be ? ParseTemporalCalendarString(identifier).
-        identifier = parse_temporal_calendar_string(global_object, identifier);
+        auto parsed_identifier = parse_temporal_calendar_string(global_object, identifier);
         if (vm.exception())
             return {};
+        identifier = move(*parsed_identifier);
     }
 
     // 4. Return ? CreateTemporalCalendar(identifier).
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp
index 5341da3d94..9f847d8651 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp
@@ -196,7 +196,7 @@ JS_DEFINE_NATIVE_FUNCTION(InstantPrototype::round)
         return {};
 
     // 14. Let roundedNs be ? RoundTemporalInstant(instant.[[Nanoseconds]], roundingIncrement, smallestUnit, roundingMode).
-    auto* rounded_ns = round_temporal_instant(global_object, instant->nanoseconds(), rounding_increment, smallest_unit, rounding_mode);
+    auto* rounded_ns = round_temporal_instant(global_object, instant->nanoseconds(), rounding_increment, smallest_unit, *rounding_mode);
     if (vm.exception())
         return {};