diff --git a/phpstan.neon b/phpstan.neon
index c839c3fa..db37782f 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,4 +1,4 @@
 parameters:
-  level: 5
+  level: 6
   paths:
     - src
diff --git a/src/Collection/TalkCollection.php b/src/Collection/TalkCollection.php
index 7389990f..a4e31795 100644
--- a/src/Collection/TalkCollection.php
+++ b/src/Collection/TalkCollection.php
@@ -7,17 +7,27 @@ namespace App\Collection;
 use Carbon\Carbon;
 use Illuminate\Support\Collection;
 
+/**
+ * @template TKey of array-key
+ * @template TValue
+ */
 final class TalkCollection extends Collection
 {
     private const DATE_FORMAT = 'Y-m-d';
     private const KEY_EVENTS = 'events';
     private const KEY_EVENT_DATE = 'date';
 
+    /**
+     * @return self<TKey, TValue>
+     */
     public function getEvents(): self
     {
         return $this->flatMap(fn($talk): array => (array) $talk[self::KEY_EVENTS]);
     }
 
+    /**
+     * @return self<TKey, TValue>
+     */
     public function onlyPastTalks(): self
     {
         $today = Carbon::today()->format(self::DATE_FORMAT);
diff --git a/src/TwigExtension/TalkExtension.php b/src/TwigExtension/TalkExtension.php
index 0c538b39..a300e771 100644
--- a/src/TwigExtension/TalkExtension.php
+++ b/src/TwigExtension/TalkExtension.php
@@ -9,6 +9,10 @@ use Illuminate\Support\Collection;
 use Twig\Extension\AbstractExtension;
 use Twig\TwigFunction;
 
+/**
+ * @template TKey of array-key
+ * @template TValue
+ */
 final class TalkExtension extends AbstractExtension
 {
     public function getFunctions()
@@ -19,6 +23,9 @@ final class TalkExtension extends AbstractExtension
         ];
     }
 
+    /**
+     * @param TValue $talk
+     */
     public function getLastEventDate($talk): ?string
     {
         $events = new Collection($talk['events']);
@@ -26,11 +33,19 @@ final class TalkExtension extends AbstractExtension
         return $events->pluck('date')->sort()->last();
     }
 
+    /**
+     * @param iterable<int, TValue> $talks
+     */
     public function getPastTalkCount(iterable $talks = []): int
     {
         return $this->getEventsFromTalks($talks)->count();
     }
 
+    /**
+     * @param iterable<int, TValue> $talks
+     *
+     * @return TalkCollection<int, TValue>
+     */
     private function getEventsFromTalks(iterable $talks): TalkCollection
     {
         $talkCollection = new TalkCollection($talks);