diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
index 95c885384c..2301017b29 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
@@ -732,7 +732,7 @@ String build_iso_month_code(u8 month)
 }
 
 // 12.1.37 ResolveISOMonth ( fields ), https://tc39.es/proposal-temporal/#sec-temporal-resolveisomonth
-double resolve_iso_month(GlobalObject& global_object, Object& fields)
+double resolve_iso_month(GlobalObject& global_object, Object const& fields)
 {
     auto& vm = global_object.vm();
 
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
index d2ed6df29a..0f592e6c44 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
@@ -64,7 +64,7 @@ u8 to_iso_day_of_week(i32 year, u8 month, u8 day);
 u16 to_iso_day_of_year(i32 year, u8 month, u8 day);
 u8 to_iso_week_of_year(i32 year, u8 month, u8 day);
 String build_iso_month_code(u8 month);
-double resolve_iso_month(GlobalObject&, Object& fields);
+double resolve_iso_month(GlobalObject&, Object const& fields);
 Optional<ISODate> iso_date_from_fields(GlobalObject&, Object const& fields, Object const& options);
 Optional<ISOYearMonth> iso_year_month_from_fields(GlobalObject&, Object const& fields, Object const& options);
 Optional<ISOMonthDay> iso_month_day_from_fields(GlobalObject&, Object const& fields, Object const& options);