Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 17204)
+++ wp-includes/functions.php	(working copy)
@@ -1422,7 +1422,7 @@
 			$base = $parts[0] . '?';
 			$query = $parts[1];
 		}
-	} elseif ( !empty( $protocol ) || strpos( $uri, '=' ) === false ) {
+	} elseif ( !empty( $protocol ) || !preg_match( '/[\?&].+=/', $uri ) ) {
 		$base = $uri . '?';
 		$query = '';
 	} else {