diff --git a/Userland/Libraries/LibJS/Runtime/AbstractOperations.h b/Userland/Libraries/LibJS/Runtime/AbstractOperations.h
index 07a45fc051..7c0a9cac83 100644
--- a/Userland/Libraries/LibJS/Runtime/AbstractOperations.h
+++ b/Userland/Libraries/LibJS/Runtime/AbstractOperations.h
@@ -136,6 +136,35 @@ ThrowCompletionOr<T*> ordinary_create_from_constructor(GlobalObject& global_obje
     return global_object.heap().allocate<T>(global_object, forward<Args>(args)..., *prototype);
 }
 
+// 14.1 MergeLists ( a, b ), https://tc39.es/proposal-temporal/#sec-temporal-mergelists
+template<typename T>
+Vector<T> merge_lists(Vector<T> const& a, Vector<T> const& b)
+{
+    // 1. Let merged be a new empty List.
+    Vector<T> merged;
+
+    // 2. For each element element of a, do
+    for (auto const& element : a) {
+        // a. If merged does not contain element, then
+        if (!merged.contains_slow(element)) {
+            // i. Append element to merged.
+            merged.append(element);
+        }
+    }
+
+    // 3. For each element element of b, do
+    for (auto const& element : b) {
+        // a. If merged does not contain element, then
+        if (!merged.contains_slow(element)) {
+            // i. Append element to merged.
+            merged.append(element);
+        }
+    }
+
+    // 4. Return merged.
+    return merged;
+}
+
 // x modulo y, https://tc39.es/ecma262/#eqn-modulo
 template<typename T, typename U>
 auto modulo(T x, U y) requires(IsArithmetic<T>, IsArithmetic<U>)
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
index 24baa84d9d..dbd0dc6c62 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
@@ -997,32 +997,4 @@ ThrowCompletionOr<Object*> default_merge_calendar_fields(GlobalObject& global_ob
     return merged;
 }
 
-// 12.2.41 MergeLists ( a, b ), https://tc39.es/proposal-temporal/#sec-temporal-mergelists
-Vector<String> merge_lists(Vector<String> const& a, Vector<String> const& b)
-{
-    // 1. Let merged be a new empty List.
-    Vector<String> merged;
-
-    // 2. For each element element of a, do
-    for (auto const& element : a) {
-        // a. If merged does not contain element, then
-        if (!merged.contains_slow(element)) {
-            // i. Append element to merged.
-            merged.append(element);
-        }
-    }
-
-    // 3. For each element element of b, do
-    for (auto const& element : b) {
-        // a. If merged does not contain element, then
-        if (!merged.contains_slow(element)) {
-            // i. Append element to merged.
-            merged.append(element);
-        }
-    }
-
-    // 4. Return merged.
-    return merged;
-}
-
 }
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
index 040a6a7e75..bada3ded72 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
@@ -74,6 +74,5 @@ u8 iso_month(Object& temporal_object);
 String iso_month_code(Object& temporal_object);
 u8 iso_day(Object& temporal_object);
 ThrowCompletionOr<Object*> default_merge_calendar_fields(GlobalObject&, Object const& fields, Object const& additional_fields);
-Vector<String> merge_lists(Vector<String> const& a, Vector<String> const& b);
 
 }
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainMonthDayPrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainMonthDayPrototype.cpp
index 4413ce794b..8f274343d0 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainMonthDayPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainMonthDayPrototype.cpp
@@ -5,6 +5,7 @@
  */
 
 #include <AK/TypeCasts.h>
+#include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/Temporal/AbstractOperations.h>
 #include <LibJS/Runtime/Temporal/Calendar.h>
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp
index 68bea0ea69..cf2abb4d57 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp
@@ -5,6 +5,7 @@
  */
 
 #include <AK/TypeCasts.h>
+#include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/Array.h>
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/Temporal/AbstractOperations.h>