diff --git a/package.json b/package.json
index a6539f5..622003e 100644
--- a/package.json
+++ b/package.json
@@ -53,6 +53,6 @@
     "yggdrasil": "0.1.0"
   },
   "optionalDependencies": {
-    "ursa": "~0.8.0"
+    "ursa": "~0.9.1"
   }
 }