diff --git a/common/include/villas/graph/vertex.hpp b/common/include/villas/graph/vertex.hpp
index 2b7256dbf..54e6a332d 100644
--- a/common/include/villas/graph/vertex.hpp
+++ b/common/include/villas/graph/vertex.hpp
@@ -35,7 +35,7 @@ public:
 	}
 
 private:
-	Identifier id;
+	Identifier id = 0;
 	// HACK: how to resolve this circular type dependency?
 	std::list<std::size_t> edges;
 };