diff --git a/wp-includes/post.php b/wp-includes/post.php
index 70d650ea82..50570936c1 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -3150,8 +3150,8 @@ function wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $post_p
 		if ( $post_name_check || in_array( $slug, $feeds ) || apply_filters( 'wp_unique_post_slug_is_bad_attachment_slug', false, $slug ) ) {
 			$suffix = 2;
 			do {
-				$alt_post_name = substr ($slug, 0, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
-				$post_name_check = $wpdb->get_var( $wpdb->prepare($check_sql, $alt_post_name, $post_ID ) );
+				$alt_post_name = _truncate_post_slug( $slug, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
+				$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $alt_post_name, $post_ID ) );
 				$suffix++;
 			} while ( $post_name_check );
 			$slug = $alt_post_name;
@@ -3167,7 +3167,7 @@ function wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $post_p
 		if ( $post_name_check || in_array( $slug, $feeds ) || preg_match( "@^($wp_rewrite->pagination_base)?\d+$@", $slug )  || apply_filters( 'wp_unique_post_slug_is_bad_hierarchical_slug', false, $slug, $post_type, $post_parent ) ) {
 			$suffix = 2;
 			do {
-				$alt_post_name = substr( $slug, 0, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
+				$alt_post_name = _truncate_post_slug( $slug, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
 				$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $alt_post_name, $post_ID, $post_parent ) );
 				$suffix++;
 			} while ( $post_name_check );
@@ -3181,7 +3181,7 @@ function wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $post_p
 		if ( $post_name_check || in_array( $slug, $feeds ) || apply_filters( 'wp_unique_post_slug_is_bad_flat_slug', false, $slug, $post_type ) ) {
 			$suffix = 2;
 			do {
-				$alt_post_name = substr( $slug, 0, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
+				$alt_post_name = _truncate_post_slug( $slug, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
 				$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $alt_post_name, $post_type, $post_ID ) );
 				$suffix++;
 			} while ( $post_name_check );
@@ -3192,6 +3192,29 @@ function wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $post_p
 	return apply_filters( 'wp_unique_post_slug', $slug, $post_ID, $post_status, $post_type, $post_parent, $original_slug );
 }
 
+/**
+ * Truncates a post slug.
+ *
+ * @since 3.6.0
+ * @access private
+ * @uses utf8_uri_encode() Makes sure UTF-8 characters are properly cut and encoded.
+ *
+ * @param string $slug The slug to truncate.
+ * @param int $length Max length of the slug.
+ * @return string The truncated slug.
+ */
+function _truncate_post_slug( $slug, $length = 200 ) {
+	if ( strlen( $slug ) > $length ) {
+		$decoded_slug = urldecode( $slug );
+		if ( $decoded_slug === $slug )
+			$slug = substr( $slug, 0, $length );
+		else
+			$slug = utf8_uri_encode( $decoded_slug, $length );
+	}
+
+	return rtrim( $slug, '-' );
+}
+
 /**
  * Adds tags to a post.
  *