diff --git a/buildstream/_artifactcache/artifactcache.py b/buildstream/_artifactcache/artifactcache.py
index 38500a0..00c1707 100644
--- a/buildstream/_artifactcache/artifactcache.py
+++ b/buildstream/_artifactcache/artifactcache.py
@@ -30,7 +30,7 @@
 from .. import utils
 from .. import _yaml
 
-from .cascache import CASCache, CASRemote
+from .cascache import CASCache, CASRemote, BlobNotFound
 
 
 CACHE_SIZE_FILE = "cache_size"