diff --git a/notebook/static/base/js/utils.js b/notebook/static/base/js/utils.js
index 8f54a6384..c7f51ecef 100644
--- a/notebook/static/base/js/utils.js
+++ b/notebook/static/base/js/utils.js
@@ -1039,6 +1039,11 @@ define([
         }
     };
 
+    var format_filesize = function(filesize) {
+      if (filesize) {
+        return filesize + " bytes";
+      }
+    }
 
     // javascript stores text as utf16 and string indices use "code units",
     // which stores high-codepoint characters as "surrogate pairs",
@@ -1180,6 +1185,7 @@ define([
         parse_b64_data_uri: parse_b64_data_uri,
         time: time,
         format_datetime: format_datetime,
+        format_filesize: format_filesize,
         datetime_sort_helper: datetime_sort_helper,
         dnd_contain_file: dnd_contain_file,
         js_idx_to_char_idx: js_idx_to_char_idx,
diff --git a/notebook/static/tree/js/notebooklist.js b/notebook/static/tree/js/notebooklist.js
index fb8104ec3..5e8ff1154 100644
--- a/notebook/static/tree/js/notebooklist.js
+++ b/notebook/static/tree/js/notebooklist.js
@@ -866,7 +866,7 @@ define([
         // Add in the date that the file was last modified
         item.find(".item_modified").text(utils.format_datetime(model.last_modified));
         item.find(".item_modified").attr("title", moment(model.last_modified).format("YYYY-MM-DD HH:mm"));
-        item.find(".file_size").html(model.size || " ");
+        item.find(".file_size").html(utils.format_filesize(model.size) || " ");
     };