diff --git a/AK/IntrusiveRedBlackTree.h b/AK/IntrusiveRedBlackTree.h
index 1a40804536..6b1442f1fc 100644
--- a/AK/IntrusiveRedBlackTree.h
+++ b/AK/IntrusiveRedBlackTree.h
@@ -55,6 +55,14 @@ public:
         return node_to_value(*node);
     }
 
+    Container find_smallest_not_below(K key)
+    {
+        auto* node = static_cast<TreeNode*>(BaseTree::find_smallest_not_below(this->m_root, key));
+        if (!node)
+            return nullptr;
+        return node_to_value(*node);
+    }
+
     void insert(K key, V& value)
     {
         auto& node = value.*member;
@@ -208,6 +216,7 @@ class IntrusiveRedBlackTree<K, V, NonnullRefPtr<V>, member> : public IntrusiveRe
 public:
     [[nodiscard]] NonnullRefPtr<V> find(K key) const { return IntrusiveRedBlackTree<K, V, RefPtr<V>, member>::find(key).release_nonnull(); }
     [[nodiscard]] NonnullRefPtr<V> find_largest_not_above(K key) const { return IntrusiveRedBlackTree<K, V, RefPtr<V>, member>::find_largest_not_above(key).release_nonnull(); }
+    [[nodiscard]] NonnullRefPtr<V> find_smallest_not_below(K key) const { return IntrusiveRedBlackTree<K, V, RefPtr<V>, member>::find_smallest_not_below(key).release_nonnull(); }
 };
 
 }
diff --git a/AK/RedBlackTree.h b/AK/RedBlackTree.h
index 11994bd4b4..8106b70d99 100644
--- a/AK/RedBlackTree.h
+++ b/AK/RedBlackTree.h
@@ -467,6 +467,14 @@ public:
         return &node->value;
     }
 
+    [[nodiscard]] V* find_smallest_not_below(K key)
+    {
+        auto* node = static_cast<Node*>(BaseTree::find_smallest_not_below(this->m_root, key));
+        if (!node)
+            return nullptr;
+        return &node->value;
+    }
+
     ErrorOr<void> try_insert(K key, V const& value)
     {
         return try_insert(key, V(value));