1 files changed, 1 insertions, 1 deletions
diff --git a/lib/async.js b/lib/async.js
index 08af693..3748ac0 100644
--- a/lib/async.js
+++ b/lib/async.js
@@ -510,7 +510,7 @@
     };
 
     async.auto = function (tasks, concurrency, callback) {
-        if (!callback) {
+        if (typeof arguments[1] === 'function') {
             // concurrency is optional, shift the args.
             callback = concurrency;
             concurrency = null;