diff --git a/app/render/previewautocacher.cpp b/app/render/previewautocacher.cpp
index 6189521fa..66a8c0f8a 100644
--- a/app/render/previewautocacher.cpp
+++ b/app/render/previewautocacher.cpp
@@ -386,6 +386,10 @@ void PreviewAutoCacher::ClearVideoQueue(bool wait)
     watcher->Cancel();
   }
   if (wait) {
+    // Re-copy because the above cancels may have deleted these watchers
+    vt_copy = video_tasks_;
+    sft_copy = single_frame_tasks_;
+
     for (auto it=vt_copy.cbegin(); it!=vt_copy.cend(); it++) {
       it.key()->WaitForFinished();
     }