diff --git a/include/contractor/contracted_edge_container.hpp b/include/contractor/contracted_edge_container.hpp
index febae6fbba..3b8ba93fd1 100644
--- a/include/contractor/contracted_edge_container.hpp
+++ b/include/contractor/contracted_edge_container.hpp
@@ -128,7 +128,7 @@ struct ContractedEdgeContainer
         edges.insert(edges.end(), new_edges.begin(), new_end);
         auto edges_size = edges.size();
         auto new_edges_size = std::distance(new_edges.begin(), new_end);
-        BOOST_ASSERT(static_cast<int>(edges_size) >= new_edges_size);
+        BOOST_ASSERT(static_cast<int64_t>(edges_size) >= new_edges_size);
         flags.resize(edges_size);
         std::fill(flags.begin() + edges_size - new_edges_size, flags.end(), flag);