diff --git a/extensions/package.json b/extensions/package.json
index 7b4e8171c1f..343e3053756 100644
--- a/extensions/package.json
+++ b/extensions/package.json
@@ -3,7 +3,7 @@
   "version": "0.0.1",
   "description": "Dependencies shared by all extensions",
   "dependencies": {
-    "typescript": "3.8.3"
+    "typescript": "3.9.1-rc"
   },
   "scripts": {
     "postinstall": "node ./postinstall"
diff --git a/extensions/typescript-language-features/src/features/fileConfigurationManager.ts b/extensions/typescript-language-features/src/features/fileConfigurationManager.ts
index 13faefc545d..686c35e18ed 100644
--- a/extensions/typescript-language-features/src/features/fileConfigurationManager.ts
+++ b/extensions/typescript-language-features/src/features/fileConfigurationManager.ts
@@ -179,9 +179,7 @@ export default class FileConfigurationManager extends Disposable {
 			isTypeScriptDocument(document) ? 'typescript.preferences' : 'javascript.preferences',
 			document.uri);
 
-		// `importModuleSpecifierEnding` added to `Proto.UserPreferences` in TypeScript 3.9:
-		// remove intersection type after upgrading TypeScript.
-		const preferences: Proto.UserPreferences & { importModuleSpecifierEnding?: string } = {
+		const preferences: Proto.UserPreferences = {
 			quotePreference: this.getQuoteStylePreference(config),
 			importModuleSpecifierPreference: getImportModuleSpecifierPreference(config),
 			importModuleSpecifierEnding: getImportModuleSpecifierEndingPreference(config),
diff --git a/extensions/typescript-language-features/src/features/workspaceSymbols.ts b/extensions/typescript-language-features/src/features/workspaceSymbols.ts
index e4caa5b5977..fb548abf854 100644
--- a/extensions/typescript-language-features/src/features/workspaceSymbols.ts
+++ b/extensions/typescript-language-features/src/features/workspaceSymbols.ts
@@ -56,7 +56,7 @@ class TypeScriptWorkspaceSymbolProvider implements vscode.WorkspaceSymbolProvide
 		}
 
 		const args: Proto.NavtoRequestArgs = {
-			file: file!, // TS 3.9+ supports using undefined to search all open projects
+			file,
 			searchValue: search,
 			maxResultCount: 256,
 		};
diff --git a/extensions/yarn.lock b/extensions/yarn.lock
index 83bd84cdd90..0a5236436a5 100644
--- a/extensions/yarn.lock
+++ b/extensions/yarn.lock
@@ -2,7 +2,7 @@
 # yarn lockfile v1
 
 
-typescript@3.8.3:
-  version "3.8.3"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.8.3.tgz#409eb8544ea0335711205869ec458ab109ee1061"
-  integrity sha512-MYlEfn5VrLNsgudQTVJeNaQFUAI7DkhnOjdpAp4T+ku1TfQClewlbSuTVHiA+8skNBgaf02TL/kLOvig4y3G8w==
+typescript@3.9.1-rc:
+  version "3.9.1-rc"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.1-rc.tgz#81d5a5a0a597e224b6e2af8dffb46524b2eaf5f3"
+  integrity sha512-+cPv8L2Vd4KidCotqi2wjegBZ5n47CDRUu/QiLVu2YbeXAz78hIfcai9ziBiNI6JTGTVwUqXRug2UZxDcxhvFw==