diff --git a/q.js b/q.js
index d9405fdc..a29c44f7 100644
--- a/q.js
+++ b/q.js
@@ -1502,6 +1502,10 @@ Promise.prototype.keys = function () {
 Q.all = all;
 function all(promises) {
     return when(promises, function (promises) {
+        if (typeof arguments[0].length === "undefined") {
+            throw TypeError("all() must be passed an array of promises.");
+        }
+
         var pendingCount = 0;
         var deferred = defer();
         array_reduce(promises, function (undefined, promise, index) {
diff --git a/spec/q-spec.js b/spec/q-spec.js
index f1d726eb..36d158ff 100644
--- a/spec/q-spec.js
+++ b/spec/q-spec.js
@@ -1096,6 +1096,20 @@ describe("propagation", function () {
 });
 
 describe("all", function () {
+    it("rejects if not passed an array", function() {
+        var promise = Q.defer(),
+            willBeRejected = Q.all(promise);
+
+        return willBeRejected.then(
+          function () {
+            expect(true).toBe(false);
+          },
+          function (err) {
+            expect(err.constructor).toBe(TypeError);
+          }
+        );
+    });
+
     it("fulfills when passed an empty array", function () {
         return Q.all([]);
     });