diff --git a/package.json b/package.json
index 19b63cbf..e878d09c 100644
--- a/package.json
+++ b/package.json
@@ -37,7 +37,7 @@
     "tslint": "^5.7.0",
     "typedoc": "^0.11.1",
     "typedoc-plugin-stimulus": "file:packages/typedoc-plugin-stimulus",
-    "typescript": "^2.8.1",
+    "typescript": "^2.8.4",
     "webpack": "^3.10.0"
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 880ffc26..0dbc7f2a 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -5626,9 +5626,9 @@ typescript@2.7.2:
   version "2.7.2"
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-2.7.2.tgz#2d615a1ef4aee4f574425cdff7026edf81919836"
 
-typescript@^2.8.1:
-  version "2.8.1"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-2.8.1.tgz#6160e4f8f195d5ba81d4876f9c0cc1fbc0820624"
+typescript@^2.8.4:
+  version "2.9.1"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-2.9.1.tgz#fdb19d2c67a15d11995fd15640e373e09ab09961"
 
 uglify-es@^3.3.7:
   version "3.3.9"