diff --git a/src/libstore/fetchers/parse.cc b/src/libstore/fetchers/parse.cc
index 4f7cb3c6b..a5ad14c87 100644
--- a/src/libstore/fetchers/parse.cc
+++ b/src/libstore/fetchers/parse.cc
@@ -22,8 +22,8 @@ ParsedURL parseURL(const std::string & url)
     if (std::regex_match(url, match, uriRegex)) {
         auto & base = match[1];
         std::string scheme = match[2];
-        auto authority = match[4].matched
-            ? std::optional<std::string>(match[5]) : std::nullopt;
+        auto authority = match[3].matched
+            ? std::optional<std::string>(match[3]) : std::nullopt;
         std::string path = match[4].matched ? match[4] : match[5];
         auto & query = match[6];
         auto & fragment = match[7];