diff --git a/package.json b/package.json
index b76471b..e758b95 100644
--- a/package.json
+++ b/package.json
@@ -42,7 +42,7 @@
     "hoodiecrow-imap": "^2.1.0",
     "mocha": "^7.0.1",
     "pre-commit": "^1.2.2",
-    "sinon": "^8.0.0",
+    "sinon": "^9.0.2",
     "standard": "^13.0.1",
     "webpack": "^4.33.0",
     "webpack-cli": "^3.3.3"