diff --git a/phpseclib/Crypt/Base.php b/phpseclib/Crypt/Base.php
index 4704a183..aad1eae8 100644
--- a/phpseclib/Crypt/Base.php
+++ b/phpseclib/Crypt/Base.php
@@ -1172,7 +1172,7 @@ class Base
      */
     function _encryptBlock($in)
     {
-        user_error(__METHOD__ . '() must extend by class ' . __CLASS__, E_USER_ERROR);
+        user_error(__METHOD__ . '() must extend by class ' . get_class($this), E_USER_ERROR);
     }
 
     /**
@@ -1186,7 +1186,7 @@ class Base
      */
     function _decryptBlock($in)
     {
-        user_error(__METHOD__ . '() must extend by class ' . __CLASS__, E_USER_ERROR);
+        user_error(__METHOD__ . '() must extend by class ' . get_class($this), E_USER_ERROR);
     }
 
     /**
@@ -1201,7 +1201,7 @@ class Base
      */
     function _setupKey()
     {
-        user_error(__METHOD__ . '() must extend by class ' . __CLASS__, E_USER_ERROR);
+        user_error(__METHOD__ . '() must extend by class ' . get_class($this), E_USER_ERROR);
     }
 
     /**