diff --git a/mobile/src/com/cradle/iitc_mobile/async/DownloadTile.java b/mobile/src/com/cradle/iitc_mobile/async/DownloadTile.java
index 9dc4cd93..62011d88 100644
--- a/mobile/src/com/cradle/iitc_mobile/async/DownloadTile.java
+++ b/mobile/src/com/cradle/iitc_mobile/async/DownloadTile.java
@@ -29,8 +29,15 @@ public class DownloadTile extends AsyncTask<String, Void, Boolean> {
             tileUrl = new URL(urls[0]);
             conn = tileUrl.openConnection();
             final File file = new File(mFilePath);
+            // some tiles don't have the lastModified header field set
+            // ...update tile every two month
+            final long updateTime = 2 * 30 * 24 * 60 * 60 * 1000;
+            final long systemTime = System.currentTimeMillis();
+            final long urlLM = conn.getLastModified();
+            final long fileLM = file.lastModified();
+            if (urlLM == 0 && (fileLM > systemTime - updateTime)) return true;
             // update tile if needed, else return
-            if (conn.getLastModified() < file.lastModified()) return true;
+            if (urlLM < fileLM) return true;
             InputStream is = null;
             is = conn.getInputStream();
             Log.d("writing to file: " + file.toString());