diff --git a/lib/auto.js b/lib/auto.js
index 61868070a..eca7d5311 100644
--- a/lib/auto.js
+++ b/lib/auto.js
@@ -137,7 +137,8 @@ export default function (tasks, concurrency, callback) {
         arrayEach(dependencies, function (dependencyName) {
             if (!tasks[dependencyName]) {
                 throw new Error('async.auto task `' + key +
-                    '` has a non-existent dependency in ' +
+                    '` has a non-existent dependency `' +
+                    dependencyName + '` in ' +
                     dependencies.join(', '));
             }
             addListener(dependencyName, function () {
diff --git a/mocha_test/auto.js b/mocha_test/auto.js
index 55f3b253f..e2e55f9f3 100644
--- a/mocha_test/auto.js
+++ b/mocha_test/auto.js
@@ -286,7 +286,7 @@ describe('auto', function () {
                     callback(null, 'task1');
                 }]
             });
-        }).to.throw();
+        }).to.throw(/dependency `noexist`/);
         done();
     });