diff --git a/package.json b/package.json
index 4864fa9..0a2808a 100644
--- a/package.json
+++ b/package.json
@@ -30,7 +30,7 @@
 		"@types/vinyl": "^2.0.2",
 		"@types/webpack": "^4.4.34",
 		"@types/xml2js": "^0.4.2",
-		"@types/yargs": "^10.0.1",
+		"@types/yargs": "^15.0.5",
 		"mocha": "^7.1.2"
 	},
 	"dependencies": {
@@ -45,7 +45,7 @@
 		"typescript": "^3.9.5",
 		"vinyl": "^2.1.0",
 		"xml2js": "^0.4.19",
-		"yargs": "^13.2.4"
+		"yargs": "^16.0.3"
 	},
 	"scripts": {
 		"prepare": "tsc -p ./src",
diff --git a/src/vscl.ts b/src/vscl.ts
index 84e551d..5151f02 100644
--- a/src/vscl.ts
+++ b/src/vscl.ts
@@ -20,15 +20,18 @@ let argv = yargs
 	.option('outDir', {
 		alias: 'o',
 		describe: 'The output directory. If not specified the files are overwriten in place.',
+		string: true,
 		demand: false
 	})
 	.option('rootDir', {
 		alias: 'r',
 		describe: 'The root directory of the sources. Only honored when outDir is set.',
+		string: true,
 		demand: false
 	})
 	.option('keepFilenames', {
 		describe: 'Inlines filenames when making localization calls. Only honored when rootDir is set.',
+		boolean: true,
 		demand: false
 	})
 	.argv;