diff --git a/lib/Graph.ts b/lib/Graph.ts
index 4d2c53d..24beed0 100644
--- a/lib/Graph.ts
+++ b/lib/Graph.ts
@@ -20,8 +20,8 @@ export class Graph extends Element {
   public style?: GraphStyles;
   public color?: Color;
   public directional = true;
-  public overlap?: boolean;
-  public splines?: boolean;
+  public overlap?: boolean | string;
+  public splines?: boolean | string;
   public layout?: GraphLayouts;
 
   private get attributes (): Array<{name: string; value: string}> {