diff --git a/websocket-sharp/Net/EndPointManager.cs b/websocket-sharp/Net/EndPointManager.cs
index de1af7af..f0b692ba 100644
--- a/websocket-sharp/Net/EndPointManager.cs
+++ b/websocket-sharp/Net/EndPointManager.cs
@@ -103,6 +103,8 @@ namespace WebSocketSharp.Net
 
       EndPointListener lsnr;
       if (tryGetEndPointListener (addr, port, out lsnr)) {
+        if (lsnr.IsSecure ^ pref.IsSecure)
+          throw new HttpListenerException (87, "Includes an invalid scheme.");
       }
       else {
         lsnr =
@@ -186,6 +188,9 @@ namespace WebSocketSharp.Net
       if (!tryGetEndPointListener (addr, port, out lsnr))
         return;
 
+      if (lsnr.IsSecure ^ pref.IsSecure)
+        return;
+
       lsnr.RemovePrefix (pref, listener);
     }