diff --git a/openflexure_microscope/camera/mock.py b/openflexure_microscope/camera/mock.py
index 4f614b1a..abffb221 100644
--- a/openflexure_microscope/camera/mock.py
+++ b/openflexure_microscope/camera/mock.py
@@ -192,7 +192,7 @@ class MockStreamer(BaseCamera):
         if isinstance(output, CaptureObject):
             target = output.file
         else:
-            target = target
+            target = output
 
         with self.lock:
             if isinstance(target, str):