diff --git a/src/ParallelError.php b/src/ParallelError.php
index 83c68ca4..b0c62b2c 100644
--- a/src/ParallelError.php
+++ b/src/ParallelError.php
@@ -6,7 +6,7 @@
 
 class ParallelError extends Exception
 {
-    public static function fromException($exception): ParallelError
+    public static function fromException($exception): self
     {
         return new self($exception);
     }
diff --git a/src/ParallelProcess.php b/src/ParallelProcess.php
index 71ec687f..592b0e4a 100644
--- a/src/ParallelProcess.php
+++ b/src/ParallelProcess.php
@@ -2,7 +2,6 @@
 
 namespace Spatie\Async;
 
-use Error;
 use Throwable;
 use Symfony\Component\Process\Process;
 use Spatie\Async\Output\SerializableException;
@@ -142,7 +141,7 @@ public function triggerSuccess()
         if ($this->getErrorOutput()) {
             $this->triggerError();
 
-            return null;
+            return;
         }
 
         $output = $this->getOutput();