diff --git a/src/Store/InMemoryStore.php b/src/Store/InMemoryStore.php
index 55b88ccb1..ab625e818 100644
--- a/src/Store/InMemoryStore.php
+++ b/src/Store/InMemoryStore.php
@@ -44,7 +44,7 @@
 
 final class InMemoryStore implements StreamStore
 {
-    /** @var array<0|positive-int, Message> */
+    /** @var array<positive-int, Message> */
     private array $messages = [];
 
     /** @param list<Message> $messages */
@@ -104,7 +104,7 @@ public function save(Message ...$messages): void
                     $message = $message->withHeader(new RecordedOnHeader($this->clock->now()));
                 }
 
-                $this->messages[] = $message;
+                $this->messages[$count] = $message;
             }
         });
     }
@@ -169,7 +169,7 @@ public function archive(Criteria|null $criteria = null): void
         }
     }
 
-    /** @return array<positive-int|0, Message> */
+    /** @return array<positive-int, Message> */
     private function filter(Criteria|null $criteria): array
     {
         if (!$criteria) {