diff --git a/src/schema.hpp b/src/schema.hpp
index 2059e1b..96176ab 100644
--- a/src/schema.hpp
+++ b/src/schema.hpp
@@ -73,7 +73,7 @@
     virtual bool leafEnumHasValue(const path_& location, const ModuleNodePair& node, const std::string& value) const = 0;
     virtual bool listHasKey(const path_& location, const ModuleNodePair& node, const std::string& key) const = 0;
     virtual bool nodeExists(const std::string& location, const std::string& node) const = 0;
-    virtual const std::set<std::string>& listKeys(const path_& location, const ModuleNodePair& node) const = 0;
+    virtual const std::set<std::string> listKeys(const path_& location, const ModuleNodePair& node) const = 0;
     virtual yang::LeafDataTypes leafType(const path_& location, const ModuleNodePair& node) const = 0;
     virtual std::set<std::string> childNodes(const path_& path) const = 0;