Index: src/wp-includes/formatting.php
===================================================================
--- src/wp-includes/formatting.php	(revision 31457)
+++ src/wp-includes/formatting.php	(working copy)
@@ -785,7 +785,15 @@
 			$unicode .= chr($value);
 			$unicode_length++;
 		} else {
-			if ( count( $values ) == 0 ) $num_octets = ( $value < 224 ) ? 2 : 3;
+			if ( count( $values ) == 0 ) {
+				if ( $value < 224 ) {
+					$num_octets = 2;
+				} elseif ( $value < 240 ) {
+					$num_octets = 3;
+				} else {
+					$num_octets = 4;
+				}
+			}
 
 			$values[] = $value;
 
@@ -792,14 +800,12 @@
 			if ( $length && ( $unicode_length + ($num_octets * 3) ) > $length )
 				break;
 			if ( count( $values ) == $num_octets ) {
-				if ($num_octets == 3) {
-					$unicode .= '%' . dechex($values[0]) . '%' . dechex($values[1]) . '%' . dechex($values[2]);
-					$unicode_length += 9;
-				} else {
-					$unicode .= '%' . dechex($values[0]) . '%' . dechex($values[1]);
-					$unicode_length += 6;
+				for ( $j = 0; $j < $num_octets; $j++ ) {
+					$unicode .= '%' . dechex( $values[ $j ] );
 				}
 
+				$unicode_length += $num_octets * 3;
+
 				$values = array();
 				$num_octets = 1;
 			}