diff --git a/src/lib/nfs/Connection.hxx b/src/lib/nfs/Connection.hxx
index fc9e4eb35..ad2756fe8 100644
--- a/src/lib/nfs/Connection.hxx
+++ b/src/lib/nfs/Connection.hxx
@@ -80,7 +80,7 @@ class NfsConnection {
 	DeferEvent defer_new_lease;
 	CoarseTimerEvent mount_timeout_event;
 
-	std::string server, export_name;
+	const std::string server, export_name;
 
 	nfs_context *context;