diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index d32793b6a..d170d7223 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -76,7 +76,7 @@ StorePath writeDerivation(ref<Store> store,
     const Derivation & drv, std::string_view name, RepairFlag repair = NoRepair);
 
 /* Read a derivation from a file. */
-Derivation parseDerivation(const Store & store, string && s);
+Derivation parseDerivation(const Store & store, std::string && s);
 
 // FIXME: remove
 bool isDerivation(const string & fileName);