diff --git a/lib/async.js b/lib/async.js
index a13f83520..50f7a2806 100644
--- a/lib/async.js
+++ b/lib/async.js
@@ -478,6 +478,17 @@
                 }
             };
             var requires = task.slice(0, Math.abs(task.length - 1)) || [];
+            // prevent dead-locks
+            var len = requires.length;
+            var dep;
+            while (len--) {
+                if (!(dep = tasks[requires[len]])) {
+                    throw new Error('Has inexistant dependency');
+                }
+                if (_isArray(dep) && !!~dep.indexOf(k)) {
+                    throw new Error('Has cyclic dependencies');
+                }
+            }
             var ready = function () {
                 return _reduce(requires, function (a, x) {
                     return (a && results.hasOwnProperty(x));
diff --git a/test/test-async.js b/test/test-async.js
index 7529f1ff9..adada4785 100755
--- a/test/test-async.js
+++ b/test/test-async.js
@@ -580,6 +580,33 @@ exports['auto modifying results causes final callback to run early'] = function(
     });
 };
 
+// Issue 263 on github: https://github.com/caolan/async/issues/263
+exports['auto prevent dead-locks due to inexistant dependencies'] = function(test) {
+    test.throws(function () {
+        async.auto({
+            task1: ['noexist', function(callback, results){
+                callback(null, 'task1');
+            }]
+        });
+    }, Error);
+    test.done();
+};
+
+// Issue 263 on github: https://github.com/caolan/async/issues/263
+exports['auto prevent dead-locks due to cyclic dependencies'] = function(test) {
+    test.throws(function () {
+        async.auto({
+            task1: ['task2', function(callback, results){
+                callback(null, 'task1');
+            }],
+            task2: ['task1', function(callback, results){
+                callback(null, 'task2');
+            }]
+        });
+    }, Error);
+    test.done();
+};
+
 // Issue 306 on github: https://github.com/caolan/async/issues/306
 exports['retry when attempt succeeds'] = function(test) {
     var failed = 3