diff --git a/threejs/three.d.ts b/threejs/three.d.ts
index 02179ff15..111a7fc9b 100644
--- a/threejs/three.d.ts
+++ b/threejs/three.d.ts
@@ -3674,7 +3674,7 @@ declare module THREE {
         /**
          * Adds v to this vector.
          */
-        add(a: Object): Vector3;
+        add(a: Vector): Vector3;
         addScalar(s: number): Vector3;
 
         /**
@@ -5759,4 +5759,4 @@ declare module THREE {
 
 declare module 'three' {
     export=THREE;
-}
\ No newline at end of file
+}