diff --git a/src/diff/dijkstra.rs b/src/diff/dijkstra.rs
index 68f3e1ce66..dbca6ac02e 100644
--- a/src/diff/dijkstra.rs
+++ b/src/diff/dijkstra.rs
@@ -123,7 +123,7 @@ pub fn mark_syntax<'a>(
     let size_hint = lhs_node_count * rhs_node_count;
 
     let start = Vertex::new(lhs_syntax, rhs_syntax);
-    let vertex_arena = Bump::with_capacity(size_hint);
+    let vertex_arena = Bump::with_capacity(size_hint * std::mem::size_of::<Vertex>());
 
     let route = shortest_path(start, &vertex_arena, size_hint, graph_limit)?;