Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 11666)
+++ wp-includes/functions.php	(working copy)
@@ -3222,7 +3222,7 @@
 /**
  * Gives a nicely formatted list of timezone strings // temporary! Not in final
  *
- * @param string $selectedzone - which zone should be the selected one
+ * @param $selected_zone string Selected Zone
  *
  */
 function wp_timezone_choice( $selected_zone ) {
@@ -3320,7 +3320,7 @@
 		$structure[] = '<option ' . $selected . 'value="' . esc_attr( $value ) . '">' . esc_html( $display ) . "</option>";
 		
 		// Close continent optgroup
-		if ( !empty( $zone['city'] ) && isset( $zonen[$key + 1] ) && $zonen[$key + 1]['continent'] !== $zone['continent'] ) {
+		if ( !empty( $zone['city'] ) && ( !isset($zonen[$key + 1]) || (isset( $zonen[$key + 1] ) && $zonen[$key + 1]['continent'] !== $zone['continent']) ) ) {
 			$structure[] = '</optgroup>';
 		}
 	}