diff --git a/mnet/lib.php b/mnet/lib.php
index e62fd865e94..e878964b72c 100644
--- a/mnet/lib.php
+++ b/mnet/lib.php
@@ -269,7 +269,7 @@ function mnet_encrypt_message($message, $remote_certificate) {
     $symmetric_keys = array();
 
     //        passed by ref ->     &$encryptedstring &$symmetric_keys
-    $bool = openssl_seal($message, $encryptedstring, $symmetric_keys, array($publickey));
+    $bool = openssl_seal($message, $encryptedstring, $symmetric_keys, array($publickey), 'RC4');
     $message = $encryptedstring;
     $symmetrickey = array_pop($symmetric_keys);
 
diff --git a/mnet/xmlrpc/client.php b/mnet/xmlrpc/client.php
index 502048bdd8d..7cedc742d5c 100644
--- a/mnet/xmlrpc/client.php
+++ b/mnet/xmlrpc/client.php
@@ -201,7 +201,8 @@ class mnet_xmlrpc_client {
         $decryptedenvelope = '';
 
         //                                          &$decryptedenvelope
-        $isOpen = openssl_open(base64_decode($data), $decryptedenvelope, base64_decode($key), $this->mnet->get_private_key());
+        $isOpen = openssl_open(base64_decode($data), $decryptedenvelope, base64_decode($key),
+            $this->mnet->get_private_key(), 'RC4');
 
         if (!$isOpen) {
             // Decryption failed... let's try our archived keys
@@ -214,7 +215,7 @@ class mnet_xmlrpc_client {
             }
             foreach($openssl_history as $keyset) {
                 $keyresource = openssl_pkey_get_private($keyset['keypair_PEM']);
-                $isOpen      = openssl_open(base64_decode($data), $decryptedenvelope, base64_decode($key), $keyresource);
+                $isOpen      = openssl_open(base64_decode($data), $decryptedenvelope, base64_decode($key), $keyresource, 'RC4');
                 if ($isOpen) {
                     // It's an older code, sir, but it checks out
                     break;
diff --git a/mnet/xmlrpc/serverlib.php b/mnet/xmlrpc/serverlib.php
index 7744294291f..4847a833e8a 100644
--- a/mnet/xmlrpc/serverlib.php
+++ b/mnet/xmlrpc/serverlib.php
@@ -59,7 +59,7 @@ function mnet_server_strip_encryption($rawpostdata) {
     $payload          = '';    // Initialize payload var
 
     //                                          &$payload
-    $isOpen = openssl_open(base64_decode($data), $payload, base64_decode($key), $mnet->get_private_key());
+    $isOpen = openssl_open(base64_decode($data), $payload, base64_decode($key), $mnet->get_private_key(), 'RC4');
     if ($isOpen) {
         $remoteclient->was_encrypted();
         return $payload;
@@ -75,7 +75,7 @@ function mnet_server_strip_encryption($rawpostdata) {
     }
     foreach($openssl_history as $keyset) {
         $keyresource = openssl_pkey_get_private($keyset['keypair_PEM']);
-        $isOpen      = openssl_open(base64_decode($data), $payload, base64_decode($key), $keyresource);
+        $isOpen      = openssl_open(base64_decode($data), $payload, base64_decode($key), $keyresource, 'RC4');
         if ($isOpen) {
             // It's an older code, sir, but it checks out
             $remoteclient->was_encrypted();