diff --git a/src/buildstream/downloadablefilesource.py b/src/buildstream/downloadablefilesource.py
index d36da6749..17b60e419 100644
--- a/src/buildstream/downloadablefilesource.py
+++ b/src/buildstream/downloadablefilesource.py
@@ -211,7 +211,7 @@ def _ensure_mirror(self, activity_name: str):
                 # We do not use etag in case what we have in cache is
                 # not matching ref in order to be able to recover from
                 # corrupted download.
-                if self.ref and not self.is_cached():
+                if self.ref and self.is_cached():
                     # Do not re-download the file if the ETag matches.
                     etag = self._get_etag(self.ref)
                 else: