diff --git a/src/Illuminate/Collections/Collection.php b/src/Illuminate/Collections/Collection.php
index 7c3b72f29cae..73adf3606965 100644
--- a/src/Illuminate/Collections/Collection.php
+++ b/src/Illuminate/Collections/Collection.php
@@ -663,6 +663,10 @@ public function intersectByKeys($items)
     /**
      * Determine if the collection is empty or not.
      *
+     * @phpstan-assert-if-true null $this->first()
+     *
+     * @phpstan-assert-if-false !null $this->first()
+     *
      * @return bool
      */
     public function isEmpty()
diff --git a/src/Illuminate/Collections/Traits/EnumeratesValues.php b/src/Illuminate/Collections/Traits/EnumeratesValues.php
index 86e68f1e9ac4..14fc0ba399a7 100644
--- a/src/Illuminate/Collections/Traits/EnumeratesValues.php
+++ b/src/Illuminate/Collections/Traits/EnumeratesValues.php
@@ -367,6 +367,10 @@ public function ensure($type)
     /**
      * Determine if the collection is not empty.
      *
+     * @phpstan-assert-if-true !null $this->first()
+     *
+     * @phpstan-assert-if-false null $this->first()
+     *
      * @return bool
      */
     public function isNotEmpty()