diff --git a/terraform/graph_config_node_test.go b/terraform/graph_config_node_test.go
index c2b016ece1..b297c6c139 100644
--- a/terraform/graph_config_node_test.go
+++ b/terraform/graph_config_node_test.go
@@ -112,4 +112,5 @@ func TestGraphNodeConfigVariable_impl(t *testing.T) {
 	var _ dag.Vertex = new(GraphNodeConfigVariable)
 	var _ dag.NamedVertex = new(GraphNodeConfigVariable)
 	var _ graphNodeConfig = new(GraphNodeConfigVariable)
+	var _ GraphNodeVariable = new(GraphNodeConfigVariable)
 }