diff --git a/packages/casl-ability/src/PureAbility.ts b/packages/casl-ability/src/PureAbility.ts
index 769a9db2e..e5c71fa3a 100755
--- a/packages/casl-ability/src/PureAbility.ts
+++ b/packages/casl-ability/src/PureAbility.ts
@@ -19,7 +19,7 @@ export class PureAbility<
     const rules = this.rulesFor(...args);
     const subject = args[1];
 
-    for (let i = 0; i < rules.length; i++) {
+    for (let i = 0, length = rules.length; i < length; i++) {
       if (rules[i].matchesConditions(subject)) {
         return rules[i];
       }
diff --git a/packages/casl-ability/src/RuleIndex.ts b/packages/casl-ability/src/RuleIndex.ts
index 09c3fdc4a..52ee99f9a 100644
--- a/packages/casl-ability/src/RuleIndex.ts
+++ b/packages/casl-ability/src/RuleIndex.ts
@@ -178,7 +178,7 @@ export class RuleIndex<A extends Abilities, Conditions> {
     event: T,
     handler: EventHandler<EventsMap<Public<this>>[T]>
   ): Unsubscribe {
-    const head = this._events.get(event) || null;
+    const head = this._events.has(event) ? this._events.get(event) : null;
     const item = new LinkedItem(handler, head);
     this._events.set(event, item);