diff --git a/aikau/src/main/resources/alfresco/renderers/Progress.js b/aikau/src/main/resources/alfresco/renderers/Progress.js
index 2dfd192829..d60f1f72ef 100644
--- a/aikau/src/main/resources/alfresco/renderers/Progress.js
+++ b/aikau/src/main/resources/alfresco/renderers/Progress.js
@@ -344,7 +344,10 @@ define(["dojo/_base/declare",
          filesAdded = parseInt(filesAdded, 10);
          totalFiles = parseInt(totalFiles, 10);
 
-         if (!total || !done || !filesAdded || !totalFiles)
+         // 0 is a legal numeric value (e.g. initial "start" progress)
+         // can't use simple truthy vs non-truthy check
+         if (isNaN(total) || total < 0 || isNaN(done) || done < 0 ||
+                 isNaN(filesAdded) || filesAdded < 0 || isNaN(totalFiles) || totalFiles < 0)
          {
             this.alfLog("error", "Missing required data for progress: done=" + done + 
                ", total=" + total +