diff --git a/psalm-baseline.xml b/psalm-baseline.xml
index 298b54e1..73bbf9d6 100644
--- a/psalm-baseline.xml
+++ b/psalm-baseline.xml
@@ -428,7 +428,6 @@
       <code><![CDATA[$attr->getFailure()]]></code>
       <code><![CDATA[$attr->getResult()]]></code>
       <code><![CDATA[$input->workflowType]]></code>
-      <code><![CDATA[$input->workflowType]]></code>
       <code><![CDATA[$result->getQueryResult()]]></code>
       <code><![CDATA[$this->execution]]></code>
       <code><![CDATA[$this->execution]]></code>
diff --git a/src/Internal/Client/ResponseToResultMapper.php b/src/Internal/Client/ResponseToResultMapper.php
index cad78996..1ad89104 100644
--- a/src/Internal/Client/ResponseToResultMapper.php
+++ b/src/Internal/Client/ResponseToResultMapper.php
@@ -25,7 +25,7 @@ public function __construct(
     public function mapUpdateWorkflowResponse(
         UpdateWorkflowExecutionResponse $result,
         string $updateName,
-        string $workflowType,
+        ?string $workflowType,
         WorkflowExecution $workflowExecution,
     ): StartUpdateOutput {
         $outcome = $result->getOutcome();
diff --git a/tests/Acceptance/Extra/Update/UntypedStubTest.php b/tests/Acceptance/Extra/Update/UntypedStubTest.php
index f43e7c81..ef0daee6 100644
--- a/tests/Acceptance/Extra/Update/UntypedStubTest.php
+++ b/tests/Acceptance/Extra/Update/UntypedStubTest.php
@@ -68,6 +68,19 @@ public function fetchResultWithTimeout(
         $this->assertSame(['key' => null], (array)$result, 'Workflow result contains resolved value');
     }
 
+    #[Test]
+    public function useClientRunningWorkflowStub(
+        #[Stub('Extra_Update_UntypedStub')] WorkflowStubInterface $stub,
+        WorkflowClientInterface $client,
+    ): void {
+        $untyped = $client->newUntypedRunningWorkflowStub(
+            $stub->getExecution()->getID(),
+            $stub->getExecution()->getRunID(),
+        );
+
+        $this->fetchResolvedResultAfterWorkflowCompleted($untyped);
+    }
+
     #[Test]
     public function handleUnknownUpdate(
         #[Stub('Extra_Update_UntypedStub')] WorkflowStubInterface $stub,