diff --git a/combo/settings.py b/combo/settings.py
index 5e999efe..3792b5f7 100644
--- a/combo/settings.py
+++ b/combo/settings.py
@@ -184,6 +184,8 @@ HAYSTACK_CONNECTIONS = {
     },
 }
 
+# from solr.thumbnail -- https://sorl-thumbnail.readthedocs.io/en/latest/reference/settings.html
+THUMBNAIL_PRESERVE_FORMAT = True
 
 COMBO_DEFAULT_PUBLIC_TEMPLATE = 'standard'
 COMBO_PUBLIC_TEMPLATES = {