diff --git a/index.js b/index.js
index 759e106..6570d55 100644
--- a/index.js
+++ b/index.js
@@ -95,7 +95,7 @@ const osLocale = mem(async (options = defaultOptions) => {
 	} catch (_) {}
 
 	return (locale || defaultLocale).replace(/_/, '-');
-});
+}, {cachePromiseRejection: false});
 
 module.exports = osLocale;
 
diff --git a/package.json b/package.json
index 70b74e6..9c33f49 100644
--- a/package.json
+++ b/package.json
@@ -35,11 +35,11 @@
 	],
 	"dependencies": {
 		"execa": "^1.0.0",
-		"lcid": "^2.0.0",
-		"mem": "^4.3.0"
+		"lcid": "^3.0.0",
+		"mem": "^5.0.0"
 	},
 	"devDependencies": {
-		"ava": "^1.4.1",
+		"ava": "^2.1.0",
 		"import-fresh": "^3.0.0",
 		"tsd": "^0.7.2",
 		"xo": "^0.24.0"
diff --git a/readme.md b/readme.md
index 59f181e..f03980f 100644
--- a/readme.md
+++ b/readme.md
@@ -28,11 +28,11 @@ const osLocale = require('os-locale');
 
 ## API
 
-### osLocale([options])
+### osLocale(options?)
 
 Returns a `Promise` for the locale.
 
-### osLocale.sync([options])
+### osLocale.sync(options?)
 
 Returns the locale.