diff --git a/src/Parallel/ValueObject/ParallelProcess.php b/src/Parallel/ValueObject/ParallelProcess.php
index 914f03eeacc..d9a105071ff 100644
--- a/src/Parallel/ValueObject/ParallelProcess.php
+++ b/src/Parallel/ValueObject/ParallelProcess.php
@@ -116,7 +116,11 @@ public function quit(): void
             $pipe->close();
         }
 
-        $this->encoder->end();
+        // the process can be quit before its connection is bound, e.g. on quitAll() after an error;
+        // in that case the encoder was never set
+        if (isset($this->encoder)) {
+            $this->encoder->end();
+        }
     }
 
     public function bindConnection(Decoder $decoder, Encoder $encoder): void