diff --git a/src/sdk/namespace_blob.js b/src/sdk/namespace_blob.js
index 92e689aaab..f718162e48 100644
--- a/src/sdk/namespace_blob.js
+++ b/src/sdk/namespace_blob.js
@@ -747,6 +747,7 @@ class NamespaceBlob {
             size,
             etag,
             create_time: flat_obj.lastModified,
+            last_modified_time: flat_obj.lastModified,
             content_type: flat_obj.contentType,
             xattr: modified_xattr,
             tag_count: tag_count,
diff --git a/src/sdk/namespace_cache.js b/src/sdk/namespace_cache.js
index 8e2fe59dc7..56af49caf2 100644
--- a/src/sdk/namespace_cache.js
+++ b/src/sdk/namespace_cache.js
@@ -683,6 +683,9 @@ class NamespaceCache {
                 async_get_last_modified_time: async () => {
                     const upload_res = await hub_promise;
                     const last_modified_time = (new Date(upload_res.last_modified_time)).getTime();
+                    if (isNaN(last_modified_time)) {
+                        throw new Error('Invalid last_modified_time returned from hub_promise, Expected a valid date or timestamp.');
+                    }
                     return last_modified_time;
                 },
                 upload_chunks_hook: this.update_cache_stats_hook(params.bucket),