diff --git a/wp-includes/class-json.php b/wp-includes/class-json.php
index 207c1774d7..7582609a66 100644
--- a/wp-includes/class-json.php
+++ b/wp-includes/class-json.php
@@ -1,4 +1,5 @@
 <?php
+if ( !class_exists( 'Services_JSON' ) ) :
 /* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */
 /**
  * Converts to and from JSON format.
@@ -858,3 +859,5 @@ if (class_exists('PEAR_Error')) {
 	}
 
 }
+endif;
+?>
diff --git a/wp-includes/class-simplepie.php b/wp-includes/class-simplepie.php
index a404081bec..44066a39b5 100644
--- a/wp-includes/class-simplepie.php
+++ b/wp-includes/class-simplepie.php
@@ -1,4 +1,5 @@
 <?php
+if ( !class_exists( 'SimplePie' ) ) :
 /**
  * SimplePie
  *
@@ -14997,5 +14998,5 @@ class SimplePie_Sanitize
 		}
 	}
 }
-
+endif;
 ?>
diff --git a/wp-includes/class-snoopy.php b/wp-includes/class-snoopy.php
index b1b32d2faa..f4eb4700ef 100644
--- a/wp-includes/class-snoopy.php
+++ b/wp-includes/class-snoopy.php
@@ -1,5 +1,5 @@
 <?php
-if ( !in_array('Snoopy', get_declared_classes() ) ) :
+if ( !class_exists( 'Snoopy' ) ) :
 /*************************************************
 
 Snoopy - the PHP net client