diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 86f55342d..bde147502 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -24,7 +24,7 @@ StorePath DerivationOutput::path(const Store & store, string drvName) const
     }, output);
 }
 
-const StorePath & BasicDerivation::findOutput(const Store & store, const string & id) const
+const StorePath BasicDerivation::findOutput(const Store & store, const string & id) const
 {
     auto i = outputs.find(id);
     if (i == outputs.end())
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 2515188ec..4694ec0dd 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -52,7 +52,7 @@ struct BasicDerivation
 
     /* Return the path corresponding to the output identifier `id' in
        the given derivation. */
-    const StorePath & findOutput(const Store & store, const std::string & id) const;
+    const StorePath findOutput(const Store & store, const std::string & id) const;
 
     bool isBuiltin() const;