diff --git a/include/contractor/files.hpp b/include/contractor/files.hpp
index fc52b3492..55eba978c 100644
--- a/include/contractor/files.hpp
+++ b/include/contractor/files.hpp
@@ -15,11 +15,13 @@ namespace files
 {
 
 // reads .osrm.hsgr file
-template<storage::Ownership Ownership>
-inline void readGraph(const boost::filesystem::path &path,
-                      unsigned &checksum,
-                      detail::QueryGraph<Ownership> &graph)
+template <typename QueryGraphT>
+inline void readGraph(const boost::filesystem::path &path, unsigned &checksum, QueryGraphT &graph)
 {
+    static_assert(std::is_same<QueryGraphView, QueryGraphT>::value ||
+                      std::is_same<QueryGraph, QueryGraphT>::value,
+                  "graph must be of type QueryGraph<>");
+
     const auto fingerprint = storage::io::FileReader::VerifyFingerprint;
     storage::io::FileReader reader{path, fingerprint};
 
@@ -28,18 +30,19 @@ inline void readGraph(const boost::filesystem::path &path,
 }
 
 // writes .osrm.hsgr file
-template<storage::Ownership Ownership>
-inline void writeGraph(const boost::filesystem::path &path,
-                       unsigned checksum,
-                       const detail::QueryGraph<Ownership> &graph)
+template <typename QueryGraphT>
+inline void
+writeGraph(const boost::filesystem::path &path, unsigned checksum, const QueryGraphT &graph)
 {
+    static_assert(std::is_same<QueryGraphView, QueryGraphT>::value ||
+                      std::is_same<QueryGraph, QueryGraphT>::value,
+                  "graph must be of type QueryGraph<>");
     const auto fingerprint = storage::io::FileWriter::GenerateFingerprint;
     storage::io::FileWriter writer{path, fingerprint};
 
     writer.WriteOne(checksum);
     util::serialization::write(writer, graph);
 }
-
 }
 }
 }