diff --git a/manifest.yaml b/manifest.yaml
index 4bad295..27a3e7a 100644
--- a/manifest.yaml
+++ b/manifest.yaml
@@ -8,8 +8,8 @@ dublin_core:
     description: ""
     format: text/markdown
     identifier: tn
-    issued: 2020-10-05
-    modified: 2020-10-05
+    issued: "2020-10-05"
+    modified: "2020-10-05"
     language:
         direction: ltr
         identifier: th