diff --git a/apps/routerconsole/jsp/flags.jsp b/apps/routerconsole/jsp/flags.jsp
index b88b37b464b39078823d8d6b9f34a2586dba0b74..7dcfa503980df73c9a5a6506b50f0bd01c4dcdc1 100644
--- a/apps/routerconsole/jsp/flags.jsp
+++ b/apps/routerconsole/jsp/flags.jsp
@@ -14,7 +14,7 @@
 String c = request.getParameter("c");
 if (c != null &&
     (c.length() == 2 || c.length() == 7) &&
-    c.replaceAll("[a-z_]", "").length() == 0) {
+    c.replaceAll("[a-z0-9_]", "").length() == 0) {
     java.io.OutputStream cout = response.getOutputStream();
     String base = net.i2p.I2PAppContext.getGlobalContext().getBaseDir().getAbsolutePath();
     String file = "docs" + java.io.File.separatorChar + "icons" + java.io.File.separatorChar +