diff --git a/classes/rssutils.php b/classes/rssutils.php
index 2a54de0e..d125a503 100755
--- a/classes/rssutils.php
+++ b/classes/rssutils.php
@@ -675,9 +675,13 @@ class RSSUtils {
 
 				$entry_tags = array_unique($additional_tags);
 
-				for ($i = 0; $i < count($entry_tags); $i++)
+				for ($i = 0; $i < count($entry_tags); $i++) {
 					$entry_tags[$i] = mb_strtolower($entry_tags[$i], 'utf-8');
 
+					// we don't support numeric tags, let's prefix them
+					if (is_numeric($entry_tags[$i])) $entry_tags[$i] = 't:' . $entry_tags[$i];
+				}
+
 				_debug("tags found: " . join(",", $entry_tags), $debug_enabled);
 
 				_debug("done collecting data.", $debug_enabled);