diff --git a/site/zenodo_rdm/config.py b/site/zenodo_rdm/config.py
index f3505ff1..744cefd4 100644
--- a/site/zenodo_rdm/config.py
+++ b/site/zenodo_rdm/config.py
@@ -330,11 +330,11 @@ def lock_edit_record_published_files(record):
 """Lock editing already published files (enforce record versioning)."""
 
 APP_RDM_RECORD_THUMBNAIL_SIZES = [
-    "10",
-    "50",
-    "100",
-    "250",
-    "750",
-    "1200",
+    10,
+    50,
+    100,
+    250,
+    750,
+    1200,
 ]
 """Thumbnail sizes."""