diff --git a/include/osmium/index/map/dummy.hpp b/include/osmium/index/map/dummy.hpp
index bafb81008..5cfb6ee50 100644
--- a/include/osmium/index/map/dummy.hpp
+++ b/include/osmium/index/map/dummy.hpp
@@ -63,6 +63,7 @@ namespace osmium {
 
                 const TValue get(const TId id) const override final {
                     not_found_error(id);
+                    return TValue(); // unreachable code just to avoid compile error
                 }
 
                 size_t size() const override final {