diff --git a/src/datastore_access.hpp b/src/datastore_access.hpp
index 0856d41..29253ce 100644
--- a/src/datastore_access.hpp
+++ b/src/datastore_access.hpp
@@ -23,7 +23,7 @@
     std::string message;
     std::optional<std::string> xpath;
 
-    DatastoreError(const std::string& message, const std::optional<std::string>& xpath);
+    DatastoreError(const std::string& message, const std::optional<std::string>& xpath = std::nullopt);
 };
 
 class DatastoreException : std::exception {