diff --git a/cache/lru_cache.ts b/cache/lru_cache.ts
index 27c8524f4..b5d7d294e 100644
--- a/cache/lru_cache.ts
+++ b/cache/lru_cache.ts
@@ -71,7 +71,7 @@ export class LruCache<K, V> extends Map<K, V>
 
   #pruneToMaxSize(): void {
     if (this.size > this.maxSize) {
-      this.delete(this.keys().next().value);
+      this.delete(this.keys().next().value!);
     }
   }
 
diff --git a/data_structures/unstable_bidirectional_map.ts b/data_structures/unstable_bidirectional_map.ts
index 02158e386..bb4ebf45a 100644
--- a/data_structures/unstable_bidirectional_map.ts
+++ b/data_structures/unstable_bidirectional_map.ts
@@ -219,5 +219,5 @@ export class BidirectionalMap<K, V> extends Map<K, V> {
    * assertEquals(map.toString(), "[object BidirectionalMap]");
    * ```
    */
-  readonly [Symbol.toStringTag] = "BidirectionalMap";
+  override readonly [Symbol.toStringTag] = "BidirectionalMap";
 }