diff --git a/src/library/relation_manager.cpp b/src/library/relation_manager.cpp
index 2851ae5e4..7562de887 100644
--- a/src/library/relation_manager.cpp
+++ b/src/library/relation_manager.cpp
@@ -291,7 +291,7 @@ relation_info_getter mk_relation_info_getter(environment const & env) {
         if (auto r = table.find(rop))
             return optional<relation_info>(*r);
         else
-            optional<relation_info>();
+            return optional<relation_info>();
     };
 }