diff --git a/package.json b/package.json
index b40fe2c..4284cde 100644
--- a/package.json
+++ b/package.json
@@ -46,7 +46,7 @@
     "sinon": "^6.0.0",
     "ts-loader": "^3.2.0",
     "tslint": "^5.9.1",
-    "typescript": "^2.7.2",
+    "typescript": "^3.9.3",
     "webpack": "^3.10.0"
   },
   "url": "https://github.com/Ikagaka/ukagaka-timer-event-source.js",