Index: wp-includes/capabilities.php
===================================================================
--- wp-includes/capabilities.php	(revision 18555)
+++ wp-includes/capabilities.php	(working copy)
@@ -110,7 +110,7 @@
 		$this->role_names =  array();
 		foreach ( (array) $this->roles as $role => $data ) {
 			$this->role_objects[$role] = new WP_Role( $role, $this->roles[$role]['capabilities'] );
-			$this->role_names[$role] = $this->roles[$role]['name'];
+			$this->role_names[$role] = isset( $this->roles[$role]['name'] ) ? $this->roles[$role]['name'] : '';
 		}
 	}