diff --git a/ftl/core/sync.ftl b/ftl/core/sync.ftl
index 8eac89f5d..32aafa930 100644
--- a/ftl/core/sync.ftl
+++ b/ftl/core/sync.ftl
@@ -26,6 +26,7 @@ sync-wrong-pass = AnkiWeb ID or password was incorrect; please try again.
 sync-resync-required = Please sync again. If this message keeps appearing, please post on the support site.
 sync-must-wait-for-end = Anki is currently syncing. Please wait for the sync to complete, then try again.
 sync-confirm-empty-download = Local collection has no cards. Download from AnkiWeb?
+sync-confirm-empty-upload = AnkiWeb collection has no cards. Replace it with local collection?
 sync-conflict-explanation =
     Your decks here and on AnkiWeb differ in such a way that they can't be merged together, so it's necessary to overwrite the decks on one side with the decks from the other.
     
diff --git a/qt/aqt/sync.py b/qt/aqt/sync.py
index 051baa483..9c776dddd 100644
--- a/qt/aqt/sync.py
+++ b/qt/aqt/sync.py
@@ -135,7 +135,7 @@ def full_sync(
     if out.required == out.FULL_DOWNLOAD:
         confirm_full_download(mw, server_usn, on_done)
     elif out.required == out.FULL_UPLOAD:
-        full_upload(mw, server_usn, on_done)
+        confirm_full_upload(mw, server_usn, on_done)
     else:
         button_labels: list[str] = [
             tr.sync_upload_to_ankiweb(),
@@ -170,6 +170,18 @@ def confirm_full_download(
         mw.closeAllWindows(lambda: full_download(mw, server_usn, on_done))
 
 
+def confirm_full_upload(
+    mw: aqt.main.AnkiQt, server_usn: int, on_done: Callable[[], None]
+) -> None:
+    # confirmation step required, as some users have reported an upload
+    # happening despite having their AnkiWeb collection not being empty
+    # (not reproducible - maybe a compiler bug?)
+    if not askUser(tr.sync_confirm_empty_upload()):
+        return on_done()
+    else:
+        mw.closeAllWindows(lambda: full_upload(mw, server_usn, on_done))
+
+
 def on_full_sync_timer(mw: aqt.main.AnkiQt, label: str) -> None:
     progress = mw.col.latest_progress()
     if not progress.HasField("full_sync"):