diff --git a/src/Illuminate/Collections/Collection.php b/src/Illuminate/Collections/Collection.php
index 595b54577ee6..7ff0133fbb5a 100644
--- a/src/Illuminate/Collections/Collection.php
+++ b/src/Illuminate/Collections/Collection.php
@@ -1146,7 +1146,7 @@ public function firstOrFail($key = null, $operator = null, $value = null)
             ? $this->operatorForWhere(...func_get_args())
             : $key;
 
-        $items = $this->when($filter)->filter($filter);
+        $items = $this->unless($filter == null)->filter($filter);
 
         if ($items->isEmpty()) {
             throw new ItemNotFoundException;
diff --git a/src/Illuminate/Collections/LazyCollection.php b/src/Illuminate/Collections/LazyCollection.php
index 66f7f0310d1b..7c176c0ea06d 100644
--- a/src/Illuminate/Collections/LazyCollection.php
+++ b/src/Illuminate/Collections/LazyCollection.php
@@ -1091,7 +1091,7 @@ public function firstOrFail($key = null, $operator = null, $value = null)
             : $key;
 
         return $this
-            ->when($filter)
+            ->unless($filter == null)
             ->filter($filter)
             ->take(1)
             ->collect()