diff --git a/Sources/RefResolver.swift b/Sources/RefResolver.swift
index f268ea0..517de84 100644
--- a/Sources/RefResolver.swift
+++ b/Sources/RefResolver.swift
@@ -1,7 +1,7 @@
 import Foundation
 
 func urlSplitFragment(url: String) -> (String, String) {
-  guard let hashIndex = url.index(of: "#") else {
+  guard let hashIndex = url.firstIndex(of: "#") else {
     return (url, "")
   }